Complete the Python function and make the tests pass.

from typing import List

def has_close_elements(numbers: List[float], threshold: float) -> bool:
    """ Check if in given list of numbers, are any two numbers closer to each other than
    given threshold.
    >>> has_close_elements([1.0, 2.0, 3.0], 0.5)
    False
    >>> has_close_elements([1.0, 2.8, 3.0, 4.0, 5.0, 2.0], 0.3)
    True
    """

git init -q && git config user.email polar@test && git config user.name Polar && git add -A && git commit -qm initial

cat > solution.py <<'PY'
from typing import List

def has_close_elements(numbers: List[float], threshold: float) -> bool:
    """ Check if in given list of numbers, are any two numbers closer to each other than
    given threshold.
    >>> has_close_elements([1.0, 2.0, 3.0], 0.5)
    False
    >>> has_close_elements([1.0, 2.8, 3.0, 4.0, 5.0, 2.0], 0.3)
    True
    """

    sorted_numbers = sorted(numbers)
    for i in range(len(sorted_numbers) - 1):
        if sorted_numbers[i + 1] - sorted_numbers[i] < threshold:
            return True
    return False

PY


Complete the Python function and make the tests pass.

from typing import List

def separate_paren_groups(paren_string: str) -> List[str]:
    """ Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
    separate those group into separate strings and return the list of those.
    Separate groups are balanced (each open brace is properly closed) and not nested within each other
    Ignore any spaces in the input string.
    >>> separate_paren_groups('( ) (( )) (( )( ))')
    ['()', '(())', '(()())']
    """

cat > solution.py <<'PY'
from typing import List

def separate_paren_groups(paren_string: str) -> List[str]:
    """ Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
    separate those group into separate strings and return the list of those.
    Separate groups are balanced (each open brace is properly closed) and not nested within each other
    Ignore any spaces in the input string.
    >>> separate_paren_groups('( ) (( )) (( )( ))')
    ['()', '(())', '(()())']
    """

    cnt, group, results = 0, "", []
    for ch in paren_string:
        if ch == "(": cnt += 1
        if ch == ")": cnt -= 1
        if ch != " ": group += ch
        if cnt == 0:
            if group != "": results.append(group)
            group = ""
    return results

PY


Complete the Python function and make the tests pass.

def truncate_number(number: float) -> float:
    """ Given a positive floating point number, it can be decomposed into
    and integer part (largest integer smaller than given number) and decimals
    (leftover part always smaller than 1).

    Return the decimal part of the number.
    >>> truncate_number(3.5)
    0.5
    """

cat > solution.py <<'PY'

def truncate_number(number: float) -> float:
    """ Given a positive floating point number, it can be decomposed into
    and integer part (largest integer smaller than given number) and decimals
    (leftover part always smaller than 1).

    Return the decimal part of the number.
    >>> truncate_number(3.5)
    0.5
    """

    return number - int(number)

PY


Complete the Python function and make the tests pass.

from typing import List

def below_zero(operations: List[int]) -> bool:
    """ You're given a list of deposit and withdrawal operations on a bank account that starts with
    zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
    at that point function should return True. Otherwise it should return False.
    >>> below_zero([1, 2, 3])
    False
    >>> below_zero([1, 2, -4, 5])
    True
    """

cat > solution.py <<'PY'
from typing import List

def below_zero(operations: List[int]) -> bool:
    """ You're given a list of deposit and withdrawal operations on a bank account that starts with
    zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
    at that point function should return True. Otherwise it should return False.
    >>> below_zero([1, 2, 3])
    False
    >>> below_zero([1, 2, -4, 5])
    True
    """

    account = 0
    for operation in operations:
        account += operation
        if account < 0:
            return True
    return False

PY


Complete the Python function and make the tests pass.

from typing import List

def mean_absolute_deviation(numbers: List[float]) -> float:
    """ For a given list of input numbers, calculate Mean Absolute Deviation
    around the mean of this dataset.
    Mean Absolute Deviation is the average absolute difference between each
    element and a centerpoint (mean in this case):
    MAD = average | x - x_mean |
    >>> mean_absolute_deviation([1.0, 2.0, 3.0, 4.0])
    1.0
    """

cat > solution.py <<'PY'
from typing import List

def mean_absolute_deviation(numbers: List[float]) -> float:
    """ For a given list of input numbers, calculate Mean Absolute Deviation
    around the mean of this dataset.
    Mean Absolute Deviation is the average absolute difference between each
    element and a centerpoint (mean in this case):
    MAD = average | x - x_mean |
    >>> mean_absolute_deviation([1.0, 2.0, 3.0, 4.0])
    1.0
    """

    mean = sum(numbers) / len(numbers)
    return sum(abs(x - mean) for x in numbers) / len(numbers)

PY


Complete the Python function and make the tests pass.

from typing import List

def intersperse(numbers: List[int], delimeter: int) -> List[int]:
    """ Insert a number 'delimeter' between every two consecutive elements of input list `numbers'
    >>> intersperse([], 4)
    []
    >>> intersperse([1, 2, 3], 4)
    [1, 4, 2, 4, 3]
    """

cat > solution.py <<'PY'
from typing import List

def intersperse(numbers: List[int], delimeter: int) -> List[int]:
    """ Insert a number 'delimeter' between every two consecutive elements of input list `numbers'
    >>> intersperse([], 4)
    []
    >>> intersperse([1, 2, 3], 4)
    [1, 4, 2, 4, 3]
    """

    res = []
    for i in range(len(numbers)):
        res.append(numbers[i])
        if i != len(numbers) - 1:
            res.append(delimeter)
    return res

PY


Complete the Python function and make the tests pass.

from typing import List

def parse_nested_parens(paren_string: str) -> List[int]:
    """ Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
    For each of the group, output the deepest level of nesting of parentheses.
    E.g. (()()) has maximum two levels of nesting while ((())) has three.

    >>> parse_nested_parens('(()()) ((())) () ((())()())')
    [2, 3, 1, 3]
    """

cat > solution.py <<'PY'
from typing import List

def parse_nested_parens(paren_string: str) -> List[int]:
    """ Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
    For each of the group, output the deepest level of nesting of parentheses.
    E.g. (()()) has maximum two levels of nesting while ((())) has three.

    >>> parse_nested_parens('(()()) ((())) () ((())()())')
    [2, 3, 1, 3]
    """

    def count_depth(s: str) -> int:
        max_depth, cnt = 0, 0
        for ch in s:
            if ch == "(": cnt += 1
            if ch == ")": cnt -= 1
            max_depth = max(max_depth, cnt)
        return max_depth

    return [count_depth(s) for s in paren_string.split(" ") if s != ""]

PY


Complete the Python function and make the tests pass.

from typing import List

def filter_by_substring(strings: List[str], substring: str) -> List[str]:
    """ Filter an input list of strings only for ones that contain given substring
    >>> filter_by_substring([], 'a')
    []
    >>> filter_by_substring(['abc', 'bacd', 'cde', 'array'], 'a')
    ['abc', 'bacd', 'array']
    """

cat > solution.py <<'PY'
from typing import List

def filter_by_substring(strings: List[str], substring: str) -> List[str]:
    """ Filter an input list of strings only for ones that contain given substring
    >>> filter_by_substring([], 'a')
    []
    >>> filter_by_substring(['abc', 'bacd', 'cde', 'array'], 'a')
    ['abc', 'bacd', 'array']
    """

    return list(filter(lambda s: substring in s, strings))

PY


Complete the Python function and make the tests pass.

from typing import List, Tuple

def sum_product(numbers: List[int]) -> Tuple[int, int]:
    """ For a given list of integers, return a tuple consisting of a sum and a product of all the integers in a list.
    Empty sum should be equal to 0 and empty product should be equal to 1.
    >>> sum_product([])
    (0, 1)
    >>> sum_product([1, 2, 3, 4])
    (10, 24)
    """

cat > solution.py <<'PY'
from typing import List, Tuple

def sum_product(numbers: List[int]) -> Tuple[int, int]:
    """ For a given list of integers, return a tuple consisting of a sum and a product of all the integers in a list.
    Empty sum should be equal to 0 and empty product should be equal to 1.
    >>> sum_product([])
    (0, 1)
    >>> sum_product([1, 2, 3, 4])
    (10, 24)
    """

    s, p = 0, 1
    for number in numbers:
        s += number
        p *= number
    return s, p

PY


Complete the Python function and make the tests pass.

from typing import List, Tuple

def rolling_max(numbers: List[int]) -> List[int]:
    """ From a given list of integers, generate a list of rolling maximum element found until given moment
    in the sequence.
    >>> rolling_max([1, 2, 3, 2, 3, 4, 2])
    [1, 2, 3, 3, 3, 4, 4]
    """

cat > solution.py <<'PY'
from typing import List, Tuple

def rolling_max(numbers: List[int]) -> List[int]:
    """ From a given list of integers, generate a list of rolling maximum element found until given moment
    in the sequence.
    >>> rolling_max([1, 2, 3, 2, 3, 4, 2])
    [1, 2, 3, 3, 3, 4, 4]
    """

    return [max(numbers[:(i+1)]) for i in range(len(numbers))]

PY


Complete the Python function and make the tests pass.

def is_palindrome(string: str) -> bool:
    """ Test if given string is a palindrome """
    return string == string[::-1]

def make_palindrome(string: str) -> str:
    """ Find the shortest palindrome that begins with a supplied string.
    Algorithm idea is simple:
    - Find the longest postfix of supplied string that is a palindrome.
    - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
    >>> make_palindrome('')
    ''
    >>> make_palindrome('cat')
    'catac'
    >>> make_palindrome('cata')
    'catac'
    """

cat > solution.py <<'PY'

def is_palindrome(string: str) -> bool:
    """ Test if given string is a palindrome """
    return string == string[::-1]

def make_palindrome(string: str) -> str:
    """ Find the shortest palindrome that begins with a supplied string.
    Algorithm idea is simple:
    - Find the longest postfix of supplied string that is a palindrome.
    - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
    >>> make_palindrome('')
    ''
    >>> make_palindrome('cat')
    'catac'
    >>> make_palindrome('cata')
    'catac'
    """

    if is_palindrome(string):
        return string
    for i in range(len(string)):
        if is_palindrome(string[i:]):
            return string + string[i-1::-1]

PY


Complete the Python function and make the tests pass.

from typing import List

def string_xor(a: str, b: str) -> str:
    """ Input are two strings a and b consisting only of 1s and 0s.
    Perform binary XOR on these inputs and return result also as a string.
    >>> string_xor('010', '110')
    '100'
    """

cat > solution.py <<'PY'
from typing import List

def string_xor(a: str, b: str) -> str:
    """ Input are two strings a and b consisting only of 1s and 0s.
    Perform binary XOR on these inputs and return result also as a string.
    >>> string_xor('010', '110')
    '100'
    """

    return "".join(str(int(a[i]) ^ int(b[i])) for i in range(len(a)))

PY


Complete the Python function and make the tests pass.

from typing import List, Optional

def longest(strings: List[str]) -> Optional[str]:
    """ Out of list of strings, return the longest one. Return the first one in case of multiple
    strings of the same length. Return None in case the input list is empty.
    >>> longest([])

    >>> longest(['a', 'b', 'c'])
    'a'
    >>> longest(['a', 'bb', 'ccc'])
    'ccc'
    """

cat > solution.py <<'PY'
from typing import List, Optional

def longest(strings: List[str]) -> Optional[str]:
    """ Out of list of strings, return the longest one. Return the first one in case of multiple
    strings of the same length. Return None in case the input list is empty.
    >>> longest([])

    >>> longest(['a', 'b', 'c'])
    'a'
    >>> longest(['a', 'bb', 'ccc'])
    'ccc'
    """

    if not strings:
        return None

    maxlen = max(len(x) for x in strings)
    for s in strings:
        if len(s) == maxlen:
            return s

PY


Complete the Python function and make the tests pass.

def greatest_common_divisor(a: int, b: int) -> int:
    """ Return a greatest common divisor of two integers a and b
    >>> greatest_common_divisor(3, 5)
    1
    >>> greatest_common_divisor(25, 15)
    5
    """

cat > solution.py <<'PY'

def greatest_common_divisor(a: int, b: int) -> int:
    """ Return a greatest common divisor of two integers a and b
    >>> greatest_common_divisor(3, 5)
    1
    >>> greatest_common_divisor(25, 15)
    5
    """

    def query_gcd(a: int, b: int) -> int:
        return a if b == 0 else query_gcd(b, a % b)
    return query_gcd(a, b)

PY


Complete the Python function and make the tests pass.

from typing import List

def all_prefixes(string: str) -> List[str]:
    """ Return list of all prefixes from shortest to longest of the input string
    >>> all_prefixes('abc')
    ['a', 'ab', 'abc']
    """

cat > solution.py <<'PY'
from typing import List

def all_prefixes(string: str) -> List[str]:
    """ Return list of all prefixes from shortest to longest of the input string
    >>> all_prefixes('abc')
    ['a', 'ab', 'abc']
    """

    return [string[:(i + 1)] for i in range(len(string))]

PY


Complete the Python function and make the tests pass.

def string_sequence(n: int) -> str:
    """ Return a string containing space-delimited numbers starting from 0 upto n inclusive.
    >>> string_sequence(0)
    '0'
    >>> string_sequence(5)
    '0 1 2 3 4 5'
    """

cat > solution.py <<'PY'

def string_sequence(n: int) -> str:
    """ Return a string containing space-delimited numbers starting from 0 upto n inclusive.
    >>> string_sequence(0)
    '0'
    >>> string_sequence(5)
    '0 1 2 3 4 5'
    """

    return " ".join(map(str, range(n + 1)))

PY


Complete the Python function and make the tests pass.

def count_distinct_characters(string: str) -> int:
    """ Given a string, find out how many distinct characters (regardless of case) does it consist of
    >>> count_distinct_characters('xyzXYZ')
    3
    >>> count_distinct_characters('Jerry')
    4
    """

cat > solution.py <<'PY'

def count_distinct_characters(string: str) -> int:
    """ Given a string, find out how many distinct characters (regardless of case) does it consist of
    >>> count_distinct_characters('xyzXYZ')
    3
    >>> count_distinct_characters('Jerry')
    4
    """

    return len(set(string.lower()))

PY


Complete the Python function and make the tests pass.

from typing import List

def parse_music(music_string: str) -> List[int]:
    """ Input to this function is a string representing musical notes in a special ASCII format.
    Your task is to parse this string and return list of integers corresponding to how many beats does each
    not last.

    Here is a legend:
    'o' - whole note, lasts four beats
    'o|' - half note, lasts two beats
    '.|' - quater note, lasts one beat

    >>> parse_music('o o| .| o| o| .| .| .| .| o o')
    [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
    """

cat > solution.py <<'PY'
from typing import List

def parse_music(music_string: str) -> List[int]:
    """ Input to this function is a string representing musical notes in a special ASCII format.
    Your task is to parse this string and return list of integers corresponding to how many beats does each
    not last.

    Here is a legend:
    'o' - whole note, lasts four beats
    'o|' - half note, lasts two beats
    '.|' - quater note, lasts one beat

    >>> parse_music('o o| .| o| o| .| .| .| .| o o')
    [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
    """

    def count_beats(note: str) -> int:
        if note == "o": return 4
        elif note == "o|": return 2
        elif note == ".|": return 1

    if music_string == "": return []
    return list(map(count_beats, music_string.split(" ")))

PY


Complete the Python function and make the tests pass.

def how_many_times(string: str, substring: str) -> int:
    """ Find how many times a given substring can be found in the original string. Count overlaping cases.
    >>> how_many_times('', 'a')
    0
    >>> how_many_times('aaa', 'a')
    3
    >>> how_many_times('aaaa', 'aa')
    3
    """

cat > solution.py <<'PY'

def how_many_times(string: str, substring: str) -> int:
    """ Find how many times a given substring can be found in the original string. Count overlaping cases.
    >>> how_many_times('', 'a')
    0
    >>> how_many_times('aaa', 'a')
    3
    >>> how_many_times('aaaa', 'aa')
    3
    """

    occurences = 0
    for i in range(len(string)):
        if string[i:].startswith(substring):
            occurences += 1
    return occurences

PY


Complete the Python function and make the tests pass.

from typing import List

def sort_numbers(numbers: str) -> str:
    """ Input is a space-delimited string of numberals from 'zero' to 'nine'.
    Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight' and 'nine'.
    Return the string with numbers sorted from smallest to largest
    >>> sort_numbers('three one five')
    'one three five'
    """

cat > solution.py <<'PY'
from typing import List

def sort_numbers(numbers: str) -> str:
    """ Input is a space-delimited string of numberals from 'zero' to 'nine'.
    Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight' and 'nine'.
    Return the string with numbers sorted from smallest to largest
    >>> sort_numbers('three one five')
    'one three five'
    """

    to_int = {'zero': 0, 'one': 1, 'two': 2, 'three': 3, 'four': 4, 'five': 5, 'six': 6, 'seven': 7, 'eight': 8, 'nine': 9}

    if numbers == "": return ""
    return " ".join(sorted(numbers.split(" "), key=lambda n: to_int[n]))

PY


Complete the Python function and make the tests pass.

from typing import List, Tuple

def find_closest_elements(numbers: List[float]) -> Tuple[float, float]:
    """ From a supplied list of numbers (of length at least two) select and return two that are the closest to each
    other and return them in order (smaller number, larger number).
    >>> find_closest_elements([1.0, 2.0, 3.0, 4.0, 5.0, 2.2])
    (2.0, 2.2)
    >>> find_closest_elements([1.0, 2.0, 3.0, 4.0, 5.0, 2.0])
    (2.0, 2.0)
    """

cat > solution.py <<'PY'
from typing import List, Tuple

def find_closest_elements(numbers: List[float]) -> Tuple[float, float]:
    """ From a supplied list of numbers (of length at least two) select and return two that are the closest to each
    other and return them in order (smaller number, larger number).
    >>> find_closest_elements([1.0, 2.0, 3.0, 4.0, 5.0, 2.2])
    (2.0, 2.2)
    >>> find_closest_elements([1.0, 2.0, 3.0, 4.0, 5.0, 2.0])
    (2.0, 2.0)
    """

    numbers.sort()
    min_diff = float("inf")
    min_pair = None
    for l, r in zip(numbers[:-1], numbers[1:]):
        diff = r - l
        if diff < min_diff:
            min_diff = diff
            min_pair = (l, r)
    return min_pair

PY


Complete the Python function and make the tests pass.

from typing import List

def rescale_to_unit(numbers: List[float]) -> List[float]:
    """ Given list of numbers (of at least two elements), apply a linear transform to that list,
    such that the smallest number will become 0 and the largest will become 1
    >>> rescale_to_unit([1.0, 2.0, 3.0, 4.0, 5.0])
    [0.0, 0.25, 0.5, 0.75, 1.0]
    """

cat > solution.py <<'PY'
from typing import List

def rescale_to_unit(numbers: List[float]) -> List[float]:
    """ Given list of numbers (of at least two elements), apply a linear transform to that list,
    such that the smallest number will become 0 and the largest will become 1
    >>> rescale_to_unit([1.0, 2.0, 3.0, 4.0, 5.0])
    [0.0, 0.25, 0.5, 0.75, 1.0]
    """

    ma, mi = max(numbers), min(numbers)
    k = 1 / (ma - mi)
    return list(map(lambda x: (x - mi) * k, numbers))

PY


Complete the Python function and make the tests pass.

from typing import List, Any

def filter_integers(values: List[Any]) -> List[int]:
    """ Filter given list of any python values only for integers
    >>> filter_integers(['a', 3.14, 5])
    [5]
    >>> filter_integers([1, 2, 3, 'abc', {}, []])
    [1, 2, 3]
    """

cat > solution.py <<'PY'
from typing import List, Any

def filter_integers(values: List[Any]) -> List[int]:
    """ Filter given list of any python values only for integers
    >>> filter_integers(['a', 3.14, 5])
    [5]
    >>> filter_integers([1, 2, 3, 'abc', {}, []])
    [1, 2, 3]
    """

    return list(filter(lambda x: type(x) == int, values))

PY


Complete the Python function and make the tests pass.

def strlen(string: str) -> int:
    """ Return length of given string
    >>> strlen('')
    0
    >>> strlen('abc')
    3
    """

cat > solution.py <<'PY'

def strlen(string: str) -> int:
    """ Return length of given string
    >>> strlen('')
    0
    >>> strlen('abc')
    3
    """

    return len(string)

PY


Complete the Python function and make the tests pass.

def largest_divisor(n: int) -> int:
    """ For a given number n, find the largest number that divides n evenly, smaller than n
    >>> largest_divisor(15)
    5
    """

cat > solution.py <<'PY'

def largest_divisor(n: int) -> int:
    """ For a given number n, find the largest number that divides n evenly, smaller than n
    >>> largest_divisor(15)
    5
    """

    for i in range(2, n):
        if n % i == 0: return n // i
    return 1

PY


Complete the Python function and make the tests pass.

from typing import List

def factorize(n: int) -> List[int]:
    """ Return list of prime factors of given integer in the order from smallest to largest.
    Each of the factors should be listed number of times corresponding to how many times it appeares in factorization.
    Input number should be equal to the product of all factors
    >>> factorize(8)
    [2, 2, 2]
    >>> factorize(25)
    [5, 5]
    >>> factorize(70)
    [2, 5, 7]
    """

cat > solution.py <<'PY'
from typing import List

def factorize(n: int) -> List[int]:
    """ Return list of prime factors of given integer in the order from smallest to largest.
    Each of the factors should be listed number of times corresponding to how many times it appeares in factorization.
    Input number should be equal to the product of all factors
    >>> factorize(8)
    [2, 2, 2]
    >>> factorize(25)
    [5, 5]
    >>> factorize(70)
    [2, 5, 7]
    """

    import math
    fact = []
    i = 2
    while i <= int(math.sqrt(n) + 1):
        if n % i == 0:
            fact.append(i)
            n //= i
        else:
            i += 1

    if n > 1:
        fact.append(n)
    return fact

PY


Complete the Python function and make the tests pass.

from typing import List

def remove_duplicates(numbers: List[int]) -> List[int]:
    """ From a list of integers, remove all elements that occur more than once.
    Keep order of elements left the same as in the input.
    >>> remove_duplicates([1, 2, 3, 2, 4])
    [1, 3, 4]
    """

cat > solution.py <<'PY'
from typing import List

def remove_duplicates(numbers: List[int]) -> List[int]:
    """ From a list of integers, remove all elements that occur more than once.
    Keep order of elements left the same as in the input.
    >>> remove_duplicates([1, 2, 3, 2, 4])
    [1, 3, 4]
    """

    num_cnt = dict()
    for number in numbers:
        if number not in num_cnt:
            num_cnt[number] = 0
        num_cnt[number] += 1
    return [number for number in numbers if num_cnt[number] == 1]

PY


Complete the Python function and make the tests pass.

def flip_case(string: str) -> str:
    """ For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
    >>> flip_case('Hello')
    'hELLO'
    """

cat > solution.py <<'PY'

def flip_case(string: str) -> str:
    """ For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
    >>> flip_case('Hello')
    'hELLO'
    """

    return "".join(map(lambda x: x.swapcase(), string))

PY


Complete the Python function and make the tests pass.

from typing import List

def concatenate(strings: List[str]) -> str:
    """ Concatenate list of strings into a single string
    >>> concatenate([])
    ''
    >>> concatenate(['a', 'b', 'c'])
    'abc'
    """

cat > solution.py <<'PY'
from typing import List

def concatenate(strings: List[str]) -> str:
    """ Concatenate list of strings into a single string
    >>> concatenate([])
    ''
    >>> concatenate(['a', 'b', 'c'])
    'abc'
    """

    return "".join(strings)

PY


Complete the Python function and make the tests pass.

from typing import List

def filter_by_prefix(strings: List[str], prefix: str) -> List[str]:
    """ Filter an input list of strings only for ones that start with a given prefix.
    >>> filter_by_prefix([], 'a')
    []
    >>> filter_by_prefix(['abc', 'bcd', 'cde', 'array'], 'a')
    ['abc', 'array']
    """

cat > solution.py <<'PY'
from typing import List

def filter_by_prefix(strings: List[str], prefix: str) -> List[str]:
    """ Filter an input list of strings only for ones that start with a given prefix.
    >>> filter_by_prefix([], 'a')
    []
    >>> filter_by_prefix(['abc', 'bcd', 'cde', 'array'], 'a')
    ['abc', 'array']
    """

    return list(filter(lambda x: x.startswith(prefix), strings))

PY


Complete the Python function and make the tests pass.

def get_positive(l: list):
    """Return only positive numbers in the list.
    >>> get_positive([-1, 2, -4, 5, 6])
    [2, 5, 6]
    >>> get_positive([5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10])
    [5, 3, 2, 3, 9, 123, 1]
    """

cat > solution.py <<'PY'

def get_positive(l: list):
    """Return only positive numbers in the list.
    >>> get_positive([-1, 2, -4, 5, 6])
    [2, 5, 6]
    >>> get_positive([5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10])
    [5, 3, 2, 3, 9, 123, 1]
    """

    return list(filter(lambda x: x > 0, l))

PY


Complete the Python function and make the tests pass.

def is_prime(n):
    """Return true if a given number is prime, and false otherwise.
    >>> is_prime(6)
    False
    >>> is_prime(101)
    True
    >>> is_prime(11)
    True
    >>> is_prime(13441)
    True
    >>> is_prime(61)
    True
    >>> is_prime(4)
    False
    >>> is_prime(1)
    False
    """

cat > solution.py <<'PY'

def is_prime(n):
    """Return true if a given number is prime, and false otherwise.
    >>> is_prime(6)
    False
    >>> is_prime(101)
    True
    >>> is_prime(11)
    True
    >>> is_prime(13441)
    True
    >>> is_prime(61)
    True
    >>> is_prime(4)
    False
    >>> is_prime(1)
    False
    """

    if n <= 1: return False
    n_sqrt = 1
    while n_sqrt ** 2 < n: n_sqrt += 1
    for i in range(2, min(n_sqrt + 1, n)):
        if n % i == 0:
            return False
    return True

PY


Complete the Python function and make the tests pass.

import math

def poly(xs: list, x: float):
    """
    Evaluates polynomial with coefficients xs at point x.
    return xs[0] + xs[1] * x + xs[1] * x^2 + .... xs[n] * x^n
    """
    return sum([coeff * math.pow(x, i) for i, coeff in enumerate(xs)])

def find_zero(xs: list):
    """ xs are coefficients of a polynomial.
    find_zero find x such that poly(x) = 0.
    find_zero returns only only zero point, even if there are many.
    Moreover, find_zero only takes list xs having even number of coefficients
    and largest non zero coefficient as it guarantees
    a solution.
    >>> round(find_zero([1, 2]), 2) # f(x) = 1 + 2x
    -0.5
    >>> round(find_zero([-6, 11, -6, 1]), 2) # (x - 1) * (x - 2) * (x - 3) = -6 + 11x - 6x^2 + x^3
    1.0
    """

cat > solution.py <<'PY'
import math

def poly(xs: list, x: float):
    """
    Evaluates polynomial with coefficients xs at point x.
    return xs[0] + xs[1] * x + xs[1] * x^2 + .... xs[n] * x^n
    """
    return sum([coeff * math.pow(x, i) for i, coeff in enumerate(xs)])

def find_zero(xs: list):
    """ xs are coefficients of a polynomial.
    find_zero find x such that poly(x) = 0.
    find_zero returns only only zero point, even if there are many.
    Moreover, find_zero only takes list xs having even number of coefficients
    and largest non zero coefficient as it guarantees
    a solution.
    >>> round(find_zero([1, 2]), 2) # f(x) = 1 + 2x
    -0.5
    >>> round(find_zero([-6, 11, -6, 1]), 2) # (x - 1) * (x - 2) * (x - 3) = -6 + 11x - 6x^2 + x^3
    1.0
    """

    dxs = [xs[i] * i for i in range(1, len(xs))]
    def func(x):
        return poly(xs, x)
    def derivative(x):
        return poly(dxs, x)

    x, tol = 0, 1e-5
    for _ in range(1000):
        fx = func(x)
        dfx = derivative(x)
        if abs(fx) < tol: break
        x = x - fx / dfx

    return x

PY


Complete the Python function and make the tests pass.

def sort_third(l: list):
    """This function takes a list l and returns a list l' such that
    l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
    to the values of the corresponding indicies of l, but sorted.
    >>> sort_third([1, 2, 3])
    [1, 2, 3]
    >>> sort_third([5, 6, 3, 4, 8, 9, 2])
    [2, 6, 3, 4, 8, 9, 5]
    """

cat > solution.py <<'PY'

def sort_third(l: list):
    """This function takes a list l and returns a list l' such that
    l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
    to the values of the corresponding indicies of l, but sorted.
    >>> sort_third([1, 2, 3])
    [1, 2, 3]
    >>> sort_third([5, 6, 3, 4, 8, 9, 2])
    [2, 6, 3, 4, 8, 9, 5]
    """

    third = [l[i] for i in range(len(l)) if i % 3 == 0]
    third.sort()
    return [third[i // 3] if i % 3 == 0 else l[i] for i in range(len(l))]

PY


Complete the Python function and make the tests pass.

def unique(l: list):
    """Return sorted unique elements in a list
    >>> unique([5, 3, 5, 2, 3, 3, 9, 0, 123])
    [0, 2, 3, 5, 9, 123]
    """

cat > solution.py <<'PY'

def unique(l: list):
    """Return sorted unique elements in a list
    >>> unique([5, 3, 5, 2, 3, 3, 9, 0, 123])
    [0, 2, 3, 5, 9, 123]
    """

    return sorted(set(l))

PY


Complete the Python function and make the tests pass.

def max_element(l: list):
    """Return maximum element in the list.
    >>> max_element([1, 2, 3])
    3
    >>> max_element([5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10])
    123
    """

cat > solution.py <<'PY'

def max_element(l: list):
    """Return maximum element in the list.
    >>> max_element([1, 2, 3])
    3
    >>> max_element([5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10])
    123
    """

    return max(l)

PY


Complete the Python function and make the tests pass.

def fizz_buzz(n: int):
    """Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
    >>> fizz_buzz(50)
    0
    >>> fizz_buzz(78)
    2
    >>> fizz_buzz(79)
    3
    """

cat > solution.py <<'PY'

def fizz_buzz(n: int):
    """Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
    >>> fizz_buzz(50)
    0
    >>> fizz_buzz(78)
    2
    >>> fizz_buzz(79)
    3
    """

    cnt = 0
    for i in range(n):
        if i % 11 == 0 or i % 13 == 0:
            cnt += len(list(filter(lambda c: c == "7", str(i))))
    return cnt

PY


Complete the Python function and make the tests pass.

def sort_even(l: list):
    """This function takes a list l and returns a list l' such that
    l' is identical to l in the odd indicies, while its values at the even indicies are equal
    to the values of the even indicies of l, but sorted.
    >>> sort_even([1, 2, 3])
    [1, 2, 3]
    >>> sort_even([5, 6, 3, 4])
    [3, 6, 5, 4]
    """

cat > solution.py <<'PY'

def sort_even(l: list):
    """This function takes a list l and returns a list l' such that
    l' is identical to l in the odd indicies, while its values at the even indicies are equal
    to the values of the even indicies of l, but sorted.
    >>> sort_even([1, 2, 3])
    [1, 2, 3]
    >>> sort_even([5, 6, 3, 4])
    [3, 6, 5, 4]
    """

    even = [l[i] for i in range(len(l)) if i % 2 == 0]
    even.sort()
    return [even[i // 2] if i % 2 == 0 else l[i] for i in range(len(l))]

PY


Complete the Python function and make the tests pass.

def encode_cyclic(s: str):
    """
    returns encoded string by cycling groups of three characters.
    """
    # split string to groups. Each of length 3.
    groups = [s[(3 * i):min((3 * i + 3), len(s))] for i in range((len(s) + 2) // 3)]
    # cycle elements in each group. Unless group has fewer elements than 3.
    groups = [(group[1:] + group[0]) if len(group) == 3 else group for group in groups]
    return "".join(groups)

def decode_cyclic(s: str):
    """
    takes as input string encoded with encode_cyclic function. Returns decoded string.
    """

cat > solution.py <<'PY'

def encode_cyclic(s: str):
    """
    returns encoded string by cycling groups of three characters.
    """
    # split string to groups. Each of length 3.
    groups = [s[(3 * i):min((3 * i + 3), len(s))] for i in range((len(s) + 2) // 3)]
    # cycle elements in each group. Unless group has fewer elements than 3.
    groups = [(group[1:] + group[0]) if len(group) == 3 else group for group in groups]
    return "".join(groups)

def decode_cyclic(s: str):
    """
    takes as input string encoded with encode_cyclic function. Returns decoded string.
    """

    groups = [s[(3 * i):min((3 * i + 3), len(s))] for i in range((len(s) + 2) // 3)]
    groups = [(group[2] + group[:2]) if len(group) == 3 else group for group in groups]
    return "".join(groups)

PY


Complete the Python function and make the tests pass.

def prime_fib(n: int):
    """
    prime_fib returns n-th number that is a Fibonacci number and it's also prime.
    >>> prime_fib(1)
    2
    >>> prime_fib(2)
    3
    >>> prime_fib(3)
    5
    >>> prime_fib(4)
    13
    >>> prime_fib(5)
    89
    """

cat > solution.py <<'PY'

def prime_fib(n: int):
    """
    prime_fib returns n-th number that is a Fibonacci number and it's also prime.
    >>> prime_fib(1)
    2
    >>> prime_fib(2)
    3
    >>> prime_fib(3)
    5
    >>> prime_fib(4)
    13
    >>> prime_fib(5)
    89
    """

    import random
    def miller_rabin(n, k=10):
        """Test if n is prime using the Miller-Rabin primality test."""
        if n < 2:
            return False
        if n == 2 or n == 3:
            return True
        if n % 2 == 0:
            return False

        r = 0
        d = n - 1
        while d % 2 == 0:
            r += 1
            d //= 2

        for _ in range(k):
            a = random.randint(2, n - 2)
            x = pow(a, d, n)
            if x == 1 or x == n - 1:
                continue
            for _ in range(r - 1):
                x = pow(x, 2, n)
                if x == n - 1:
                    break
            else:
                return False

        return True

    c_prime = 0
    a, b = 0, 1
    while c_prime < n:
        a, b = b, a + b
        if miller_rabin(b):
            c_prime += 1
    return b

PY


Complete the Python function and make the tests pass.

def triples_sum_to_zero(l: list):
    """
    triples_sum_to_zero takes a list of integers as an input.
    it returns True if there are three distinct elements in the list that
    sum to zero, and False otherwise.

    >>> triples_sum_to_zero([1, 3, 5, 0])
    False
    >>> triples_sum_to_zero([1, 3, -2, 1])
    True
    >>> triples_sum_to_zero([1, 2, 3, 7])
    False
    >>> triples_sum_to_zero([2, 4, -5, 3, 9, 7])
    True
    >>> triples_sum_to_zero([1])
    False
    """

cat > solution.py <<'PY'

def triples_sum_to_zero(l: list):
    """
    triples_sum_to_zero takes a list of integers as an input.
    it returns True if there are three distinct elements in the list that
    sum to zero, and False otherwise.

    >>> triples_sum_to_zero([1, 3, 5, 0])
    False
    >>> triples_sum_to_zero([1, 3, -2, 1])
    True
    >>> triples_sum_to_zero([1, 2, 3, 7])
    False
    >>> triples_sum_to_zero([2, 4, -5, 3, 9, 7])
    True
    >>> triples_sum_to_zero([1])
    False
    """

    for i in range(len(l)):
        for j in range(len(l)):
            for k in range(len(l)):
                if i != j and i != k and j != k and l[i] + l[j] + l[k] == 0:
                    return True
    return False

PY


Complete the Python function and make the tests pass.

def car_race_collision(n: int):
    """
    Imagine a road that's a perfectly straight infinitely long line.
    n cars are driving left to right;  simultaneously, a different set of n cars
    are driving right to left.   The two sets of cars start out being very far from
    each other.  All cars move in the same speed.  Two cars are said to collide
    when a car that's moving left to right hits a car that's moving right to left.
    However, the cars are infinitely sturdy and strong; as a result, they continue moving
    in their trajectory as if they did not collide.

    This function outputs the number of such collisions.
    """

cat > solution.py <<'PY'

def car_race_collision(n: int):
    """
    Imagine a road that's a perfectly straight infinitely long line.
    n cars are driving left to right;  simultaneously, a different set of n cars
    are driving right to left.   The two sets of cars start out being very far from
    each other.  All cars move in the same speed.  Two cars are said to collide
    when a car that's moving left to right hits a car that's moving right to left.
    However, the cars are infinitely sturdy and strong; as a result, they continue moving
    in their trajectory as if they did not collide.

    This function outputs the number of such collisions.
    """

    return n ** 2

PY


Complete the Python function and make the tests pass.

def incr_list(l: list):
    """Return list with elements incremented by 1.
    >>> incr_list([1, 2, 3])
    [2, 3, 4]
    >>> incr_list([5, 3, 5, 2, 3, 3, 9, 0, 123])
    [6, 4, 6, 3, 4, 4, 10, 1, 124]
    """

cat > solution.py <<'PY'

def incr_list(l: list):
    """Return list with elements incremented by 1.
    >>> incr_list([1, 2, 3])
    [2, 3, 4]
    >>> incr_list([5, 3, 5, 2, 3, 3, 9, 0, 123])
    [6, 4, 6, 3, 4, 4, 10, 1, 124]
    """

    return [x + 1 for x in l]

PY


Complete the Python function and make the tests pass.

def pairs_sum_to_zero(l):
    """
    pairs_sum_to_zero takes a list of integers as an input.
    it returns True if there are two distinct elements in the list that
    sum to zero, and False otherwise.
    >>> pairs_sum_to_zero([1, 3, 5, 0])
    False
    >>> pairs_sum_to_zero([1, 3, -2, 1])
    False
    >>> pairs_sum_to_zero([1, 2, 3, 7])
    False
    >>> pairs_sum_to_zero([2, 4, -5, 3, 5, 7])
    True
    >>> pairs_sum_to_zero([1])
    False
    """

cat > solution.py <<'PY'

def pairs_sum_to_zero(l):
    """
    pairs_sum_to_zero takes a list of integers as an input.
    it returns True if there are two distinct elements in the list that
    sum to zero, and False otherwise.
    >>> pairs_sum_to_zero([1, 3, 5, 0])
    False
    >>> pairs_sum_to_zero([1, 3, -2, 1])
    False
    >>> pairs_sum_to_zero([1, 2, 3, 7])
    False
    >>> pairs_sum_to_zero([2, 4, -5, 3, 5, 7])
    True
    >>> pairs_sum_to_zero([1])
    False
    """

    for i in range(len(l)):
        for j in range(len(l)):
            if i != j and l[i] + l[j] == 0:
                return True
    return False

PY


Complete the Python function and make the tests pass.

def change_base(x: int, base: int):
    """Change numerical base of input number x to base.
    return string representation after the conversion.
    base numbers are less than 10.
    >>> change_base(8, 3)
    '22'
    >>> change_base(8, 2)
    '1000'
    >>> change_base(7, 2)
    '111'
    """

cat > solution.py <<'PY'

def change_base(x: int, base: int):
    """Change numerical base of input number x to base.
    return string representation after the conversion.
    base numbers are less than 10.
    >>> change_base(8, 3)
    '22'
    >>> change_base(8, 2)
    '1000'
    >>> change_base(7, 2)
    '111'
    """

    if x == 0: return "0"
    ret = ""
    while x != 0:
        ret = str(x % base) + ret
        x //= base
    return ret

PY


Complete the Python function and make the tests pass.

def triangle_area(a, h):
    """Given length of a side and high return area for a triangle.
    >>> triangle_area(5, 3)
    7.5
    """

cat > solution.py <<'PY'

def triangle_area(a, h):
    """Given length of a side and high return area for a triangle.
    >>> triangle_area(5, 3)
    7.5
    """

    return a * h / 2

PY


Complete the Python function and make the tests pass.

def fib4(n: int):
    """The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
    fib4(0) -> 0
    fib4(1) -> 0
    fib4(2) -> 2
    fib4(3) -> 0
    fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
    Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
    >>> fib4(5)
    4
    >>> fib4(6)
    8
    >>> fib4(7)
    14
    """

cat > solution.py <<'PY'

def fib4(n: int):
    """The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
    fib4(0) -> 0
    fib4(1) -> 0
    fib4(2) -> 2
    fib4(3) -> 0
    fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
    Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
    >>> fib4(5)
    4
    >>> fib4(6)
    8
    >>> fib4(7)
    14
    """

    if n == 0:
        return 0
    elif n == 1:
        return 0
    elif n == 2:
        return 2
    elif n == 3:
        return 0
    else:
        a, b, c, d = 0, 0, 2, 0
        for i in range(4, n + 1):
            a, b, c, d = b, c, d, a + b + c + d
        return d

PY


Complete the Python function and make the tests pass.

def median(l: list):
    """Return median of elements in the list l.
    >>> median([3, 1, 2, 4, 5])
    3
    >>> median([-10, 4, 6, 1000, 10, 20])
    15.0
    """

cat > solution.py <<'PY'

def median(l: list):
    """Return median of elements in the list l.
    >>> median([3, 1, 2, 4, 5])
    3
    >>> median([-10, 4, 6, 1000, 10, 20])
    15.0
    """

    sorted_l = sorted(l)
    if len(l) % 2 == 1:
        return sorted_l[len(l) // 2]
    else:
        return (sorted_l[len(l) // 2 - 1] + sorted_l[len(l) // 2]) / 2

PY


Complete the Python function and make the tests pass.

def is_palindrome(text: str):
    """
    Checks if given string is a palindrome
    >>> is_palindrome('')
    True
    >>> is_palindrome('aba')
    True
    >>> is_palindrome('aaaaa')
    True
    >>> is_palindrome('zbcd')
    False
    """

cat > solution.py <<'PY'

def is_palindrome(text: str):
    """
    Checks if given string is a palindrome
    >>> is_palindrome('')
    True
    >>> is_palindrome('aba')
    True
    >>> is_palindrome('aaaaa')
    True
    >>> is_palindrome('zbcd')
    False
    """

    return text == text[::-1]

PY


Complete the Python function and make the tests pass.

def modp(n: int, p: int):
    """Return 2^n modulo p (be aware of numerics).
    >>> modp(3, 5)
    3
    >>> modp(1101, 101)
    2
    >>> modp(0, 101)
    1
    >>> modp(3, 11)
    8
    >>> modp(100, 101)
    1
    """

cat > solution.py <<'PY'

def modp(n: int, p: int):
    """Return 2^n modulo p (be aware of numerics).
    >>> modp(3, 5)
    3
    >>> modp(1101, 101)
    2
    >>> modp(0, 101)
    1
    >>> modp(3, 11)
    8
    >>> modp(100, 101)
    1
    """

    res, x = 1, 2
    while n != 0:
        if n % 2 == 1:
            res = res * x % p
        x = x * x % p
        n //= 2
    return res % p

PY


Complete the Python function and make the tests pass.

def encode_shift(s: str):
    """
    returns encoded string by shifting every character by 5 in the alphabet.
    """
    return "".join([chr(((ord(ch) + 5 - ord("a")) % 26) + ord("a")) for ch in s])

def decode_shift(s: str):
    """
    takes as input string encoded with encode_shift function. Returns decoded string.
    """

cat > solution.py <<'PY'

def encode_shift(s: str):
    """
    returns encoded string by shifting every character by 5 in the alphabet.
    """
    return "".join([chr(((ord(ch) + 5 - ord("a")) % 26) + ord("a")) for ch in s])

def decode_shift(s: str):
    """
    takes as input string encoded with encode_shift function. Returns decoded string.
    """

    return "".join([chr((ord(ch) - ord("a") - 5 + 26) % 26 + ord("a")) for ch in s])

PY


Complete the Python function and make the tests pass.

def remove_vowels(text):
    """
    remove_vowels is a function that takes string and returns string without vowels.
    >>> remove_vowels('')
    ''
    >>> remove_vowels("abcdef\nghijklm")
    'bcdf\nghjklm'
    >>> remove_vowels('abcdef')
    'bcdf'
    >>> remove_vowels('aaaaa')
    ''
    >>> remove_vowels('aaBAA')
    'B'
    >>> remove_vowels('zbcd')
    'zbcd'
    """

cat > solution.py <<'PY'

def remove_vowels(text):
    """
    remove_vowels is a function that takes string and returns string without vowels.
    >>> remove_vowels('')
    ''
    >>> remove_vowels("abcdef\nghijklm")
    'bcdf\nghjklm'
    >>> remove_vowels('abcdef')
    'bcdf'
    >>> remove_vowels('aaaaa')
    ''
    >>> remove_vowels('aaBAA')
    'B'
    >>> remove_vowels('zbcd')
    'zbcd'
    """

    return "".join(list(filter(lambda ch: ch not in "aeiouAEIOU", text)))

PY


Complete the Python function and make the tests pass.

def below_threshold(l: list, t: int):
    """Return True if all numbers in the list l are below threshold t.
    >>> below_threshold([1, 2, 4, 10], 100)
    True
    >>> below_threshold([1, 20, 4, 10], 5)
    False
    """

cat > solution.py <<'PY'

def below_threshold(l: list, t: int):
    """Return True if all numbers in the list l are below threshold t.
    >>> below_threshold([1, 2, 4, 10], 100)
    True
    >>> below_threshold([1, 20, 4, 10], 5)
    False
    """

    return all(x < t for x in l)

PY


Complete the Python function and make the tests pass.

def add(x: int, y: int):
    """Add two numbers x and y
    >>> add(2, 3)
    5
    >>> add(5, 7)
    12
    """

cat > solution.py <<'PY'

def add(x: int, y: int):
    """Add two numbers x and y
    >>> add(2, 3)
    5
    >>> add(5, 7)
    12
    """

    return x + y

PY


Complete the Python function and make the tests pass.

def same_chars(s0: str, s1: str):
    """
    Check if two words have the same characters.
    >>> same_chars('eabcdzzzz', 'dddzzzzzzzddeddabc')
    True
    >>> same_chars('abcd', 'dddddddabc')
    True
    >>> same_chars('dddddddabc', 'abcd')
    True
    >>> same_chars('eabcd', 'dddddddabc')
    False
    >>> same_chars('abcd', 'dddddddabce')
    False
    >>> same_chars('eabcdzzzz', 'dddzzzzzzzddddabc')
    False
    """

cat > solution.py <<'PY'

def same_chars(s0: str, s1: str):
    """
    Check if two words have the same characters.
    >>> same_chars('eabcdzzzz', 'dddzzzzzzzddeddabc')
    True
    >>> same_chars('abcd', 'dddddddabc')
    True
    >>> same_chars('dddddddabc', 'abcd')
    True
    >>> same_chars('eabcd', 'dddddddabc')
    False
    >>> same_chars('abcd', 'dddddddabce')
    False
    >>> same_chars('eabcdzzzz', 'dddzzzzzzzddddabc')
    False
    """

    return set(s0) == set(s1)

PY


Complete the Python function and make the tests pass.

def fib(n: int):
    """Return n-th Fibonacci number.
    >>> fib(10)
    55
    >>> fib(1)
    1
    >>> fib(8)
    21
    """

cat > solution.py <<'PY'

def fib(n: int):
    """Return n-th Fibonacci number.
    >>> fib(10)
    55
    >>> fib(1)
    1
    >>> fib(8)
    21
    """

    if n == 0: return 0
    if n <= 2: return 1
    a, b = 1, 1
    for _ in range(3, n + 1):
        a, b, = b, a + b
    return b

PY


Complete the Python function and make the tests pass.

def correct_bracketing(brackets: str):
    """ brackets is a string of "<" and ">".
    return True if every opening bracket has a corresponding closing bracket.

    >>> correct_bracketing("<")
    False
    >>> correct_bracketing("<>")
    True
    >>> correct_bracketing("<<><>>")
    True
    >>> correct_bracketing("><<>")
    False
    """

cat > solution.py <<'PY'

def correct_bracketing(brackets: str):
    """ brackets is a string of "<" and ">".
    return True if every opening bracket has a corresponding closing bracket.

    >>> correct_bracketing("<")
    False
    >>> correct_bracketing("<>")
    True
    >>> correct_bracketing("<<><>>")
    True
    >>> correct_bracketing("><<>")
    False
    """

    cnt = 0
    for x in brackets:
        if x == "<": cnt += 1
        if x == ">": cnt -= 1
        if cnt < 0: return False
    return cnt == 0

PY


Complete the Python function and make the tests pass.

def monotonic(l: list):
    """Return True is list elements are monotonically increasing or decreasing.
    >>> monotonic([1, 2, 4, 20])
    True
    >>> monotonic([1, 20, 4, 10])
    False
    >>> monotonic([4, 1, 0, -10])
    True
    """

cat > solution.py <<'PY'

def monotonic(l: list):
    """Return True is list elements are monotonically increasing or decreasing.
    >>> monotonic([1, 2, 4, 20])
    True
    >>> monotonic([1, 20, 4, 10])
    False
    >>> monotonic([4, 1, 0, -10])
    True
    """

    inc, dec = True, True
    for i in range(len(l) - 1):
        if l[i] > l[i + 1]: inc = False
        if l[i] < l[i + 1]: dec = False
    return inc or dec

PY


Complete the Python function and make the tests pass.

def common(l1: list, l2: list):
    """Return sorted unique common elements for two lists.
    >>> common([1, 4, 3, 34, 653, 2, 5], [5, 7, 1, 5, 9, 653, 121])
    [1, 5, 653]
    >>> common([5, 3, 2, 8], [3, 2])
    [2, 3]

    """

cat > solution.py <<'PY'

def common(l1: list, l2: list):
    """Return sorted unique common elements for two lists.
    >>> common([1, 4, 3, 34, 653, 2, 5], [5, 7, 1, 5, 9, 653, 121])
    [1, 5, 653]
    >>> common([5, 3, 2, 8], [3, 2])
    [2, 3]

    """

    return sorted(list(set(l1).intersection(set(l2))))

PY


Complete the Python function and make the tests pass.

def largest_prime_factor(n: int):
    """Return the largest prime factor of n. Assume n > 1 and is not a prime.
    >>> largest_prime_factor(13195)
    29
    >>> largest_prime_factor(2048)
    2
    """

cat > solution.py <<'PY'

def largest_prime_factor(n: int):
    """Return the largest prime factor of n. Assume n > 1 and is not a prime.
    >>> largest_prime_factor(13195)
    29
    >>> largest_prime_factor(2048)
    2
    """

    isprime = [True] * (n + 1)
    for i in range(2, n + 1):
        if isprime[i]:
            for j in range(i + i, n, i):
                isprime[j] = False
    for i in range(n - 1, 0, -1):
        if isprime[i] and n % i == 0:
            return i

PY


Complete the Python function and make the tests pass.

def sum_to_n(n: int):
    """sum_to_n is a function that sums numbers from 1 to n.
    >>> sum_to_n(30)
    465
    >>> sum_to_n(100)
    5050
    >>> sum_to_n(5)
    15
    >>> sum_to_n(10)
    55
    >>> sum_to_n(1)
    1
    """

cat > solution.py <<'PY'

def sum_to_n(n: int):
    """sum_to_n is a function that sums numbers from 1 to n.
    >>> sum_to_n(30)
    465
    >>> sum_to_n(100)
    5050
    >>> sum_to_n(5)
    15
    >>> sum_to_n(10)
    55
    >>> sum_to_n(1)
    1
    """

    return (n + 1) * n // 2

PY


Complete the Python function and make the tests pass.

def correct_bracketing(brackets: str):
    """ brackets is a string of "(" and ")".
    return True if every opening bracket has a corresponding closing bracket.

    >>> correct_bracketing("(")
    False
    >>> correct_bracketing("()")
    True
    >>> correct_bracketing("(()())")
    True
    >>> correct_bracketing(")(()")
    False
    """

cat > solution.py <<'PY'

def correct_bracketing(brackets: str):
    """ brackets is a string of "(" and ")".
    return True if every opening bracket has a corresponding closing bracket.

    >>> correct_bracketing("(")
    False
    >>> correct_bracketing("()")
    True
    >>> correct_bracketing("(()())")
    True
    >>> correct_bracketing(")(()")
    False
    """

    cnt = 0
    for x in brackets:
        if x == "(": cnt += 1
        if x == ")": cnt -= 1
        if cnt < 0: return False
    return cnt == 0

PY


Complete the Python function and make the tests pass.

def derivative(xs: list):
    """ xs represent coefficients of a polynomial.
    xs[0] + xs[1] * x + xs[2] * x^2 + ....
     Return derivative of this polynomial in the same form.
    >>> derivative([3, 1, 2, 4, 5])
    [1, 4, 12, 20]
    >>> derivative([1, 2, 3])
    [2, 6]
    """

cat > solution.py <<'PY'

def derivative(xs: list):
    """ xs represent coefficients of a polynomial.
    xs[0] + xs[1] * x + xs[2] * x^2 + ....
     Return derivative of this polynomial in the same form.
    >>> derivative([3, 1, 2, 4, 5])
    [1, 4, 12, 20]
    >>> derivative([1, 2, 3])
    [2, 6]
    """

    return [xs[i] * i for i in range(1, len(xs))]

PY


Complete the Python function and make the tests pass.

def fibfib(n: int):
    """The FibFib number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
    fibfib(0) == 0
    fibfib(1) == 0
    fibfib(2) == 1
    fibfib(n) == fibfib(n-1) + fibfib(n-2) + fibfib(n-3).
    Please write a function to efficiently compute the n-th element of the fibfib number sequence.
    >>> fibfib(1)
    0
    >>> fibfib(5)
    4
    >>> fibfib(8)
    24
    """

cat > solution.py <<'PY'

def fibfib(n: int):
    """The FibFib number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
    fibfib(0) == 0
    fibfib(1) == 0
    fibfib(2) == 1
    fibfib(n) == fibfib(n-1) + fibfib(n-2) + fibfib(n-3).
    Please write a function to efficiently compute the n-th element of the fibfib number sequence.
    >>> fibfib(1)
    0
    >>> fibfib(5)
    4
    >>> fibfib(8)
    24
    """

    if n == 0 or n == 1:
        return 0
    elif n == 2:
        return 1
    a, b, c = 0, 0, 1
    for _ in range(3, n + 1):
        a, b, c = b, c, a + b + c
    return c

PY


Complete the Python function and make the tests pass.

FIX = """
Add more test cases.
"""

def vowels_count(s):
    """Write a function vowels_count which takes a string representing
    a word as input and returns the number of vowels in the string.
    Vowels in this case are 'a', 'e', 'i', 'o', 'u'. Here, 'y' is also a
    vowel, but only when it is at the end of the given word.

    Example:
    >>> vowels_count("abcde")
    2
    >>> vowels_count("ACEDY")
    3
    """

cat > solution.py <<'PY'

FIX = """
Add more test cases.
"""

def vowels_count(s):
    """Write a function vowels_count which takes a string representing
    a word as input and returns the number of vowels in the string.
    Vowels in this case are 'a', 'e', 'i', 'o', 'u'. Here, 'y' is also a
    vowel, but only when it is at the end of the given word.

    Example:
    >>> vowels_count("abcde")
    2
    >>> vowels_count("ACEDY")
    3
    """

    if s == "": return 0
    cnt = len(list(filter(lambda ch: ch in "aeiouAEIOU", s)))
    if s[-1] in "yY": cnt += 1
    return cnt

PY


Complete the Python function and make the tests pass.

def circular_shift(x, shift):
    """Circular shift the digits of the integer x, shift the digits right by shift
    and return the result as a string.
    If shift > number of digits, return digits reversed.
    >>> circular_shift(12, 1)
    "21"
    >>> circular_shift(12, 2)
    "12"
    """

cat > solution.py <<'PY'

def circular_shift(x, shift):
    """Circular shift the digits of the integer x, shift the digits right by shift
    and return the result as a string.
    If shift > number of digits, return digits reversed.
    >>> circular_shift(12, 1)
    "21"
    >>> circular_shift(12, 2)
    "12"
    """

    s = str(x)
    if shift > len(s): return s[::-1]
    shift %= len(s)
    if shift == 0:
        return s
    else:
        return s[len(s) - shift:] + s[:len(s) - shift]

PY


Complete the Python function and make the tests pass.

def digitSum(s):
    """Task
    Write a function that takes a string as input and returns the sum of the upper characters only'
    ASCII codes.

    Examples:
        digitSum("") => 0
        digitSum("abAB") => 131
        digitSum("abcCd") => 67
        digitSum("helloE") => 69
        digitSum("woArBld") => 131
        digitSum("aAaaaXa") => 153
    """

cat > solution.py <<'PY'

def digitSum(s):
    """Task
    Write a function that takes a string as input and returns the sum of the upper characters only'
    ASCII codes.

    Examples:
        digitSum("") => 0
        digitSum("abAB") => 131
        digitSum("abcCd") => 67
        digitSum("helloE") => 69
        digitSum("woArBld") => 131
        digitSum("aAaaaXa") => 153
    """

    return sum([ord(ch) for ch in s if ch.isupper()])

PY


Complete the Python function and make the tests pass.

def fruit_distribution(s,n):
    """
    In this task, you will be given a string that represents a number of apples and oranges
    that are distributed in a basket of fruit this basket contains
    apples, oranges, and mango fruits. Given the string that represents the total number of
    the oranges and apples and an integer that represent the total number of the fruits
    in the basket return the number of the mango fruits in the basket.
    for examble:
    fruit_distribution("5 apples and 6 oranges", 19) ->19 - 5 - 6 = 8
    fruit_distribution("0 apples and 1 oranges",3) -> 3 - 0 - 1 = 2
    fruit_distribution("2 apples and 3 oranges", 100) -> 100 - 2 - 3 = 95
    fruit_distribution("100 apples and 1 oranges",120) -> 120 - 100 - 1 = 19
    """

cat > solution.py <<'PY'

def fruit_distribution(s,n):
    """
    In this task, you will be given a string that represents a number of apples and oranges
    that are distributed in a basket of fruit this basket contains
    apples, oranges, and mango fruits. Given the string that represents the total number of
    the oranges and apples and an integer that represent the total number of the fruits
    in the basket return the number of the mango fruits in the basket.
    for examble:
    fruit_distribution("5 apples and 6 oranges", 19) ->19 - 5 - 6 = 8
    fruit_distribution("0 apples and 1 oranges",3) -> 3 - 0 - 1 = 2
    fruit_distribution("2 apples and 3 oranges", 100) -> 100 - 2 - 3 = 95
    fruit_distribution("100 apples and 1 oranges",120) -> 120 - 100 - 1 = 19
    """

    words = s.split(" ")
    c1, c2 = int(words[0]), int(words[3])
    assert n - c1 - c2 >= 0, "invalid inputs" # $_CONTRACT_$

    return n - c1 - c2

PY


Complete the Python function and make the tests pass.

def pluck(arr):
    """
    "Given an array representing a branch of a tree that has non-negative integer nodes
    your task is to pluck one of the nodes and return it.
    The plucked node should be the node with the smallest even value.
    If multiple nodes with the same smallest even value are found return the node that has smallest index.

    The plucked node should be returned in a list, [ smalest_value, its index ],
    If there are no even values or the given array is empty, return [].

    Example 1:
        Input: [4,2,3]
        Output: [2, 1]
        Explanation: 2 has the smallest even value, and 2 has the smallest index.

    Example 2:
        Input: [1,2,3]
        Output: [2, 1]
        Explanation: 2 has the smallest even value, and 2 has the smallest index.

    Example 3:
        Input: []
        Output: []

    Example 4:
        Input: [5, 0, 3, 0, 4, 2]
        Output: [0, 1]
        Explanation: 0 is the smallest value, but  there are two zeros,
                     so we will choose the first zero, which has the smallest index.

    Constraints:
        * 1 <= nodes.length <= 10000
        * 0 <= node.value
    """

cat > solution.py <<'PY'

def pluck(arr):
    """
    "Given an array representing a branch of a tree that has non-negative integer nodes
    your task is to pluck one of the nodes and return it.
    The plucked node should be the node with the smallest even value.
    If multiple nodes with the same smallest even value are found return the node that has smallest index.

    The plucked node should be returned in a list, [ smalest_value, its index ],
    If there are no even values or the given array is empty, return [].

    Example 1:
        Input: [4,2,3]
        Output: [2, 1]
        Explanation: 2 has the smallest even value, and 2 has the smallest index.

    Example 2:
        Input: [1,2,3]
        Output: [2, 1]
        Explanation: 2 has the smallest even value, and 2 has the smallest index.

    Example 3:
        Input: []
        Output: []

    Example 4:
        Input: [5, 0, 3, 0, 4, 2]
        Output: [0, 1]
        Explanation: 0 is the smallest value, but  there are two zeros,
                     so we will choose the first zero, which has the smallest index.

    Constraints:
        * 1 <= nodes.length <= 10000
        * 0 <= node.value
    """

    if all(val % 2 == 1 for val in arr): return []
    min_even = min(filter(lambda x: x % 2 == 0, arr))
    for i in range(len(arr)):
        if arr[i] == min_even:
            return [min_even, i]

PY


Complete the Python function and make the tests pass.

def search(lst):
    '''
    You are given a non-empty list of positive integers. Return the greatest integer that is greater than
    zero, and has a frequency greater than or equal to the value of the integer itself.
    The frequency of an integer is the number of times it appears in the list.
    If no such a value exist, return -1.
    Examples:
        search([4, 1, 2, 2, 3, 1]) == 2
        search([1, 2, 2, 3, 3, 3, 4, 4, 4]) == 3
        search([5, 5, 4, 4, 4]) == -1
    '''

cat > solution.py <<'PY'

def search(lst):
    '''
    You are given a non-empty list of positive integers. Return the greatest integer that is greater than
    zero, and has a frequency greater than or equal to the value of the integer itself.
    The frequency of an integer is the number of times it appears in the list.
    If no such a value exist, return -1.
    Examples:
        search([4, 1, 2, 2, 3, 1]) == 2
        search([1, 2, 2, 3, 3, 3, 4, 4, 4]) == 3
        search([5, 5, 4, 4, 4]) == -1
    '''

    count = dict()
    for num in lst:
        if num not in count:
            count[num] = 0
        count[num] += 1
    ans = -1
    for num, cnt in count.items():
        if cnt >= num:
            ans = max(ans, num)
    return ans

PY


Complete the Python function and make the tests pass.

def strange_sort_list(lst):
    '''
    Given list of integers, return list in strange order.
    Strange sorting, is when you start with the minimum value,
    then maximum of the remaining integers, then minimum and so on.

    Examples:
    strange_sort_list([1, 2, 3, 4]) == [1, 4, 2, 3]
    strange_sort_list([5, 5, 5, 5]) == [5, 5, 5, 5]
    strange_sort_list([]) == []
    '''

cat > solution.py <<'PY'

def strange_sort_list(lst):
    '''
    Given list of integers, return list in strange order.
    Strange sorting, is when you start with the minimum value,
    then maximum of the remaining integers, then minimum and so on.

    Examples:
    strange_sort_list([1, 2, 3, 4]) == [1, 4, 2, 3]
    strange_sort_list([5, 5, 5, 5]) == [5, 5, 5, 5]
    strange_sort_list([]) == []
    '''

    sorted_list = sorted(lst)
    ans, i, j = [], 0, len(sorted_list) - 1
    while i < j:
        ans.append(sorted_list[i])
        ans.append(sorted_list[j])
        i += 1
        j -= 1
    if i == j: ans.append(sorted_list[i])
    return ans

PY


Complete the Python function and make the tests pass.

def triangle_area(a, b, c):
    '''
    Given the lengths of the three sides of a triangle. Return the area of
    the triangle rounded to 2 decimal points if the three sides form a valid triangle.
    Otherwise return -1
    Three sides make a valid triangle when the sum of any two sides is greater
    than the third side.
    Example:
    triangle_area(3, 4, 5) == 6.00
    triangle_area(1, 2, 10) == -1
    '''

cat > solution.py <<'PY'

def triangle_area(a, b, c):
    '''
    Given the lengths of the three sides of a triangle. Return the area of
    the triangle rounded to 2 decimal points if the three sides form a valid triangle.
    Otherwise return -1
    Three sides make a valid triangle when the sum of any two sides is greater
    than the third side.
    Example:
    triangle_area(3, 4, 5) == 6.00
    triangle_area(1, 2, 10) == -1
    '''

    if a + b <= c or a + c <= b or b + c <= a: return -1
    p = (a + b + c) / 2
    return round((p * (p - a) * (p - b) * (p - c)) ** 0.5, 2)

PY


Complete the Python function and make the tests pass.

def will_it_fly(q,w):
    '''
    Write a function that returns True if the object q will fly, and False otherwise.
    The object q will fly if it's balanced (it is a palindromic list) and the sum of its elements is less than or equal the maximum possible weight w.

    Example:
    will_it_fly([1, 2], 5) ➞ False
    # 1+2 is less than the maximum possible weight, but it's unbalanced.

    will_it_fly([3, 2, 3], 1) ➞ False
    # it's balanced, but 3+2+3 is more than the maximum possible weight.

    will_it_fly([3, 2, 3], 9) ➞ True
    # 3+2+3 is less than the maximum possible weight, and it's balanced.

    will_it_fly([3], 5) ➞ True
    # 3 is less than the maximum possible weight, and it's balanced.
    '''

cat > solution.py <<'PY'

def will_it_fly(q,w):
    '''
    Write a function that returns True if the object q will fly, and False otherwise.
    The object q will fly if it's balanced (it is a palindromic list) and the sum of its elements is less than or equal the maximum possible weight w.

    Example:
    will_it_fly([1, 2], 5) ➞ False
    # 1+2 is less than the maximum possible weight, but it's unbalanced.

    will_it_fly([3, 2, 3], 1) ➞ False
    # it's balanced, but 3+2+3 is more than the maximum possible weight.

    will_it_fly([3, 2, 3], 9) ➞ True
    # 3+2+3 is less than the maximum possible weight, and it's balanced.

    will_it_fly([3], 5) ➞ True
    # 3 is less than the maximum possible weight, and it's balanced.
    '''

    return q == q[::-1] and sum(q) <= w

PY


Complete the Python function and make the tests pass.

def smallest_change(arr):
    """
    Given an array arr of integers, find the minimum number of elements that
    need to be changed to make the array palindromic. A palindromic array is an array that
    is read the same backwards and forwards. In one change, you can change one element to any other element.

    For example:
    smallest_change([1,2,3,5,4,7,9,6]) == 4
    smallest_change([1, 2, 3, 4, 3, 2, 2]) == 1
    smallest_change([1, 2, 3, 2, 1]) == 0
    """

cat > solution.py <<'PY'

def smallest_change(arr):
    """
    Given an array arr of integers, find the minimum number of elements that
    need to be changed to make the array palindromic. A palindromic array is an array that
    is read the same backwards and forwards. In one change, you can change one element to any other element.

    For example:
    smallest_change([1,2,3,5,4,7,9,6]) == 4
    smallest_change([1, 2, 3, 4, 3, 2, 2]) == 1
    smallest_change([1, 2, 3, 2, 1]) == 0
    """

    arr_reversed, cnt = arr[::-1], 0
    for i in range(len(arr) // 2):
        if arr[i] != arr_reversed[i]:
            cnt += 1
    return cnt

PY


Complete the Python function and make the tests pass.

def total_match(lst1, lst2):
    '''
    Write a function that accepts two lists of strings and returns the list that has
    total number of chars in the all strings of the list less than the other list.

    if the two lists have the same number of chars, return the first list.

    Examples
    total_match([], []) ➞ []
    total_match(['hi', 'admin'], ['hI', 'Hi']) ➞ ['hI', 'Hi']
    total_match(['hi', 'admin'], ['hi', 'hi', 'admin', 'project']) ➞ ['hi', 'admin']
    total_match(['hi', 'admin'], ['hI', 'hi', 'hi']) ➞ ['hI', 'hi', 'hi']
    total_match(['4'], ['1', '2', '3', '4', '5']) ➞ ['4']
    '''

cat > solution.py <<'PY'

def total_match(lst1, lst2):
    '''
    Write a function that accepts two lists of strings and returns the list that has
    total number of chars in the all strings of the list less than the other list.

    if the two lists have the same number of chars, return the first list.

    Examples
    total_match([], []) ➞ []
    total_match(['hi', 'admin'], ['hI', 'Hi']) ➞ ['hI', 'Hi']
    total_match(['hi', 'admin'], ['hi', 'hi', 'admin', 'project']) ➞ ['hi', 'admin']
    total_match(['hi', 'admin'], ['hI', 'hi', 'hi']) ➞ ['hI', 'hi', 'hi']
    total_match(['4'], ['1', '2', '3', '4', '5']) ➞ ['4']
    '''

    c1, c2 = sum(map(lambda s: len(s), lst1)), sum(map(lambda s: len(s), lst2))
    return lst1 if c1 <= c2 else lst2

PY


Complete the Python function and make the tests pass.

def is_multiply_prime(a):
    """Write a function that returns true if the given number is the multiplication of 3 prime numbers
    and false otherwise.
    Knowing that (a) is less then 100.
    Example:
    is_multiply_prime(30) == True
    30 = 2 * 3 * 5
    """

cat > solution.py <<'PY'

def is_multiply_prime(a):
    """Write a function that returns true if the given number is the multiplication of 3 prime numbers
    and false otherwise.
    Knowing that (a) is less then 100.
    Example:
    is_multiply_prime(30) == True
    30 = 2 * 3 * 5
    """

    if a <= 1: return False
    isprime = [True] * (a + 1)
    for i in range(2, a + 1):
        if isprime[i]:
            for j in range(i + i, a + 1, i):
                isprime[j] = False
    cnt, tmp = 0, a
    for i in range(2, a + 1):
        while isprime[i] and tmp % i == 0:
            tmp //= i
            cnt += 1
    return cnt == 3

PY


Complete the Python function and make the tests pass.

def is_simple_power(x, n):
    """Your task is to write a function that returns true if a number x is a simple
    power of n and false in other cases.
    x is a simple power of n if n**int=x
    For example:
    is_simple_power(1, 4) => true
    is_simple_power(2, 2) => true
    is_simple_power(8, 2) => true
    is_simple_power(3, 2) => false
    is_simple_power(3, 1) => false
    is_simple_power(5, 3) => false
    """

cat > solution.py <<'PY'

def is_simple_power(x, n):
    """Your task is to write a function that returns true if a number x is a simple
    power of n and false in other cases.
    x is a simple power of n if n**int=x
    For example:
    is_simple_power(1, 4) => true
    is_simple_power(2, 2) => true
    is_simple_power(8, 2) => true
    is_simple_power(3, 2) => false
    is_simple_power(3, 1) => false
    is_simple_power(5, 3) => false
    """

    if x == 1: return True
    if n == 0: return x == 0
    if n == 1: return x == 1
    if n == -1: return abs(x) == 1
    p = n
    while abs(p) <= abs(x):
        if p == x: return True
        p = p * n
    return False

PY


Complete the Python function and make the tests pass.

def iscube(a):
    '''
    Write a function that takes an integer a and returns True
    if this ingeger is a cube of some integer number.
    Note: you may assume the input is always valid.
    Examples:
    iscube(1) ==> True
    iscube(2) ==> False
    iscube(-1) ==> True
    iscube(64) ==> True
    iscube(0) ==> True
    iscube(180) ==> False
    '''

cat > solution.py <<'PY'

def iscube(a):
    '''
    Write a function that takes an integer a and returns True
    if this ingeger is a cube of some integer number.
    Note: you may assume the input is always valid.
    Examples:
    iscube(1) ==> True
    iscube(2) ==> False
    iscube(-1) ==> True
    iscube(64) ==> True
    iscube(0) ==> True
    iscube(180) ==> False
    '''

    a = abs(a)
    return int(round(a ** (1. / 3))) ** 3 == a

PY


Complete the Python function and make the tests pass.

def hex_key(num):
    """You have been tasked to write a function that receives
    a hexadecimal number as a string and counts the number of hexadecimal
    digits that are primes (prime number, or a prime, is a natural number
    greater than 1 that is not a product of two smaller natural numbers).
    Hexadecimal digits are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F.
    Prime numbers are 2, 3, 5, 7, 11, 13, 17,...
    So you have to determine a number of the following digits: 2, 3, 5, 7,
    B (=decimal 11), D (=decimal 13).
    Note: you may assume the input is always correct or empty string,
    and symbols A,B,C,D,E,F are always uppercase.
    Examples:
    For num = "AB" the output should be 1.
    For num = "1077E" the output should be 2.
    For num = "ABED1A33" the output should be 4.
    For num = "123456789ABCDEF0" the output should be 6.
    For num = "2020" the output should be 2.
    """

cat > solution.py <<'PY'

def hex_key(num):
    """You have been tasked to write a function that receives
    a hexadecimal number as a string and counts the number of hexadecimal
    digits that are primes (prime number, or a prime, is a natural number
    greater than 1 that is not a product of two smaller natural numbers).
    Hexadecimal digits are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F.
    Prime numbers are 2, 3, 5, 7, 11, 13, 17,...
    So you have to determine a number of the following digits: 2, 3, 5, 7,
    B (=decimal 11), D (=decimal 13).
    Note: you may assume the input is always correct or empty string,
    and symbols A,B,C,D,E,F are always uppercase.
    Examples:
    For num = "AB" the output should be 1.
    For num = "1077E" the output should be 2.
    For num = "ABED1A33" the output should be 4.
    For num = "123456789ABCDEF0" the output should be 6.
    For num = "2020" the output should be 2.
    """

    return len(list(filter(lambda x: x in "2357BD", num)))

PY


Complete the Python function and make the tests pass.

def decimal_to_binary(decimal):
    """You will be given a number in decimal form and your task is to convert it to
    binary format. The function should return a string, with each character representing a binary
    number. Each character in the string will be '0' or '1'.

    There will be an extra couple of characters 'db' at the beginning and at the end of the string.
    The extra characters are there to help with the format.

    Examples:
    decimal_to_binary(15)   # returns "db1111db"
    decimal_to_binary(32)   # returns "db100000db"
    """

cat > solution.py <<'PY'

def decimal_to_binary(decimal):
    """You will be given a number in decimal form and your task is to convert it to
    binary format. The function should return a string, with each character representing a binary
    number. Each character in the string will be '0' or '1'.

    There will be an extra couple of characters 'db' at the beginning and at the end of the string.
    The extra characters are there to help with the format.

    Examples:
    decimal_to_binary(15)   # returns "db1111db"
    decimal_to_binary(32)   # returns "db100000db"
    """

    return "db" + bin(decimal)[2:] + "db"

PY


Complete the Python function and make the tests pass.

def is_happy(s):
    """You are given a string s.
    Your task is to check if the string is happy or not.
    A string is happy if its length is at least 3 and every 3 consecutive letters are distinct
    For example:
    is_happy(a) => False
    is_happy(aa) => False
    is_happy(abcd) => True
    is_happy(aabb) => False
    is_happy(adb) => True
    is_happy(xyy) => False
    """

cat > solution.py <<'PY'

def is_happy(s):
    """You are given a string s.
    Your task is to check if the string is happy or not.
    A string is happy if its length is at least 3 and every 3 consecutive letters are distinct
    For example:
    is_happy(a) => False
    is_happy(aa) => False
    is_happy(abcd) => True
    is_happy(aabb) => False
    is_happy(adb) => True
    is_happy(xyy) => False
    """

    if len(s) < 3: return False
    for i in range(len(s) - 2):
        if s[i] == s[i + 1] or s[i] == s[i + 2] or s[i + 1] == s[i + 2]:
            return False
    return True

PY


Complete the Python function and make the tests pass.

def numerical_letter_grade(grades):
    """It is the last week of the semester and the teacher has to give the grades
    to students. The teacher has been making her own algorithm for grading.
    The only problem is, she has lost the code she used for grading.
    She has given you a list of GPAs for some students and you have to write
    a function that can output a list of letter grades using the following table:
             GPA       |    Letter grade
              4.0                A+
            > 3.7                A
            > 3.3                A-
            > 3.0                B+
            > 2.7                B
            > 2.3                B-
            > 2.0                C+
            > 1.7                C
            > 1.3                C-
            > 1.0                D+
            > 0.7                D
            > 0.0                D-
              0.0                E

    Example:
    grade_equation([4.0, 3, 1.7, 2, 3.5]) ==> ['A+', 'B', 'C-', 'C', 'A-']
    """

cat > solution.py <<'PY'

def numerical_letter_grade(grades):
    """It is the last week of the semester and the teacher has to give the grades
    to students. The teacher has been making her own algorithm for grading.
    The only problem is, she has lost the code she used for grading.
    She has given you a list of GPAs for some students and you have to write
    a function that can output a list of letter grades using the following table:
             GPA       |    Letter grade
              4.0                A+
            > 3.7                A
            > 3.3                A-
            > 3.0                B+
            > 2.7                B
            > 2.3                B-
            > 2.0                C+
            > 1.7                C
            > 1.3                C-
            > 1.0                D+
            > 0.7                D
            > 0.0                D-
              0.0                E

    Example:
    grade_equation([4.0, 3, 1.7, 2, 3.5]) ==> ['A+', 'B', 'C-', 'C', 'A-']
    """

    def to_letter_grade(score):
      if score == 4.0:
        return "A+"
      elif score > 3.7:
        return "A"
      elif score > 3.3:
        return "A-"
      elif score > 3.0:
        return "B+"
      elif score > 2.7:
        return "B"
      elif score > 2.3:
        return "B-"
      elif score > 2.0:
        return "C+"
      elif score > 1.7:
        return "C"
      elif score > 1.3:
        return "C-"
      elif score > 1.0:
        return "D+"
      elif score > 0.7:
        return "D"
      elif score > 0.0:
        return "D-"
      else:
        return "E"

    return [to_letter_grade(x) for x in grades]

PY


Complete the Python function and make the tests pass.

def prime_length(string):
    """Write a function that takes a string and returns True if the string
    length is a prime number or False otherwise
    Examples
    prime_length('Hello') == True
    prime_length('abcdcba') == True
    prime_length('kittens') == True
    prime_length('orange') == False
    """

cat > solution.py <<'PY'

def prime_length(string):
    """Write a function that takes a string and returns True if the string
    length is a prime number or False otherwise
    Examples
    prime_length('Hello') == True
    prime_length('abcdcba') == True
    prime_length('kittens') == True
    prime_length('orange') == False
    """

    def is_prime(a):
        return not (a < 2 or any(a % x == 0 for x in range(2, int(a ** 0.5) + 1)))

    return is_prime(len(string))

PY


Complete the Python function and make the tests pass.

def starts_one_ends(n):
    """
    Given a positive integer n, return the count of the numbers of n-digit
    positive integers that start or end with 1.
    """

cat > solution.py <<'PY'

def starts_one_ends(n):
    """
    Given a positive integer n, return the count of the numbers of n-digit
    positive integers that start or end with 1.
    """

    if n == 1: return 1
    return 18 * 10 ** (n - 2)

PY


Complete the Python function and make the tests pass.

def solve(N):
    """Given a positive integer N, return the total sum of its digits in binary.

    Example
        For N = 1000, the sum of digits will be 1 the output should be "1".
        For N = 150, the sum of digits will be 6 the output should be "110".
        For N = 147, the sum of digits will be 12 the output should be "1100".

    Variables:
        @N integer
             Constraints: 0 ≤ N ≤ 10000.
    Output:
         a string of binary number
    """

cat > solution.py <<'PY'

def solve(N):
    """Given a positive integer N, return the total sum of its digits in binary.

    Example
        For N = 1000, the sum of digits will be 1 the output should be "1".
        For N = 150, the sum of digits will be 6 the output should be "110".
        For N = 147, the sum of digits will be 12 the output should be "1100".

    Variables:
        @N integer
             Constraints: 0 ≤ N ≤ 10000.
    Output:
         a string of binary number
    """

    s = sum(map(lambda x: int(x), str(N)))
    return bin(s)[2:]

PY


Complete the Python function and make the tests pass.

def add(lst):
    """Given a non-empty list of integers lst. add the even elements that are at odd indices..

    Examples:
        add([4, 2, 6, 7]) ==> 2
    """

cat > solution.py <<'PY'

def add(lst):
    """Given a non-empty list of integers lst. add the even elements that are at odd indices..

    Examples:
        add([4, 2, 6, 7]) ==> 2
    """

    s = 0
    for i in range(1, len(lst), 2):
        if lst[i] % 2 == 0:
            s += lst[i]
    return s

PY


Complete the Python function and make the tests pass.

def anti_shuffle(s):
    """
    Write a function that takes a string and returns an ordered version of it.
    Ordered version of string, is a string where all words (separated by space)
    are replaced by a new word where all the characters arranged in
    ascending order based on ascii value.
    Note: You should keep the order of words and blank spaces in the sentence.

    For example:
    anti_shuffle('Hi') returns 'Hi'
    anti_shuffle('hello') returns 'ehllo'
    anti_shuffle('Hello World!!!') returns 'Hello !!!Wdlor'
    """

cat > solution.py <<'PY'

def anti_shuffle(s):
    """
    Write a function that takes a string and returns an ordered version of it.
    Ordered version of string, is a string where all words (separated by space)
    are replaced by a new word where all the characters arranged in
    ascending order based on ascii value.
    Note: You should keep the order of words and blank spaces in the sentence.

    For example:
    anti_shuffle('Hi') returns 'Hi'
    anti_shuffle('hello') returns 'ehllo'
    anti_shuffle('Hello World!!!') returns 'Hello !!!Wdlor'
    """

    words = s.split(" ")
    return " ".join(map(lambda x: "".join(sorted(x, key=lambda ch: ord(ch))), words))

PY


Complete the Python function and make the tests pass.

def get_row(lst, x):
    """
    You are given a 2 dimensional data, as a nested lists,
    which is similar to matrix, however, unlike matrices,
    each row may contain a different number of columns.
    Given lst, and integer x, find integers x in the list,
    and return list of tuples, [(x1, y1), (x2, y2) ...] such that
    each tuple is a coordinate - (row, columns), starting with 0.
    Sort coordinates initially by rows in ascending order.
    Also, sort coordinates of the row by columns in descending order.

    Examples:
    get_row([
      [1,2,3,4,5,6],
      [1,2,3,4,1,6],
      [1,2,3,4,5,1]
    ], 1) == [(0, 0), (1, 4), (1, 0), (2, 5), (2, 0)]
    get_row([], 1) == []
    get_row([[], [1], [1, 2, 3]], 3) == [(2, 2)]
    """

cat > solution.py <<'PY'

def get_row(lst, x):
    """
    You are given a 2 dimensional data, as a nested lists,
    which is similar to matrix, however, unlike matrices,
    each row may contain a different number of columns.
    Given lst, and integer x, find integers x in the list,
    and return list of tuples, [(x1, y1), (x2, y2) ...] such that
    each tuple is a coordinate - (row, columns), starting with 0.
    Sort coordinates initially by rows in ascending order.
    Also, sort coordinates of the row by columns in descending order.

    Examples:
    get_row([
      [1,2,3,4,5,6],
      [1,2,3,4,1,6],
      [1,2,3,4,5,1]
    ], 1) == [(0, 0), (1, 4), (1, 0), (2, 5), (2, 0)]
    get_row([], 1) == []
    get_row([[], [1], [1, 2, 3]], 3) == [(2, 2)]
    """

    res = []
    for i, l in enumerate(lst):
        for j in range(len(l) - 1, -1, -1):
            if l[j] == x: res.append((i, j))
    return res

PY


Complete the Python function and make the tests pass.

def sort_array(array):
    """
    Given an array of non-negative integers, return a copy of the given array after sorting,
    you will sort the given array in ascending order if the sum( first index value, last index value) is odd,
    or sort it in descending order if the sum( first index value, last index value) is even.

    Note:
    * don't change the given array.

    Examples:
    * sort_array([]) => []
    * sort_array([5]) => [5]
    * sort_array([2, 4, 3, 0, 1, 5]) => [0, 1, 2, 3, 4, 5]
    * sort_array([2, 4, 3, 0, 1, 5, 6]) => [6, 5, 4, 3, 2, 1, 0]
    """

cat > solution.py <<'PY'

def sort_array(array):
    """
    Given an array of non-negative integers, return a copy of the given array after sorting,
    you will sort the given array in ascending order if the sum( first index value, last index value) is odd,
    or sort it in descending order if the sum( first index value, last index value) is even.

    Note:
    * don't change the given array.

    Examples:
    * sort_array([]) => []
    * sort_array([5]) => [5]
    * sort_array([2, 4, 3, 0, 1, 5]) => [0, 1, 2, 3, 4, 5]
    * sort_array([2, 4, 3, 0, 1, 5, 6]) => [6, 5, 4, 3, 2, 1, 0]
    """

    if array == []: return []
    return sorted(array, reverse=(array[0]+array[-1]) % 2 == 0)

PY


Complete the Python function and make the tests pass.

def encrypt(s):
    """Create a function encrypt that takes a string as an argument and
    returns a string encrypted with the alphabet being rotated.
    The alphabet should be rotated in a manner such that the letters
    shift down by two multiplied to two places.
    For example:
    encrypt('hi') returns 'lm'
    encrypt('asdfghjkl') returns 'ewhjklnop'
    encrypt('gf') returns 'kj'
    encrypt('et') returns 'ix'
    """

cat > solution.py <<'PY'

def encrypt(s):
    """Create a function encrypt that takes a string as an argument and
    returns a string encrypted with the alphabet being rotated.
    The alphabet should be rotated in a manner such that the letters
    shift down by two multiplied to two places.
    For example:
    encrypt('hi') returns 'lm'
    encrypt('asdfghjkl') returns 'ewhjklnop'
    encrypt('gf') returns 'kj'
    encrypt('et') returns 'ix'
    """

    d = 'abcdefghijklmnopqrstuvwxyz'
    return "".join(map(lambda ch: chr((ord(ch) - ord("a") + 4) % 26 + ord("a")) if ch in d else ch, s))

PY


Complete the Python function and make the tests pass.

def next_smallest(lst):
    """
    You are given a list of integers.
    Write a function next_smallest() that returns the 2nd smallest element of the list.
    Return None if there is no such element.

    next_smallest([1, 2, 3, 4, 5]) == 2
    next_smallest([5, 1, 4, 3, 2]) == 2
    next_smallest([]) == None
    next_smallest([1, 1]) == None
    """

cat > solution.py <<'PY'

def next_smallest(lst):
    """
    You are given a list of integers.
    Write a function next_smallest() that returns the 2nd smallest element of the list.
    Return None if there is no such element.

    next_smallest([1, 2, 3, 4, 5]) == 2
    next_smallest([5, 1, 4, 3, 2]) == 2
    next_smallest([]) == None
    next_smallest([1, 1]) == None
    """

    if len(lst) <= 1: return None
    sorted_list = sorted(lst)
    for x in sorted_list:
        if x != sorted_list[0]:
            return x

PY


Complete the Python function and make the tests pass.

def is_bored(S):
    """
    You'll be given a string of words, and your task is to count the number
    of boredoms. A boredom is a sentence that starts with the word "I".
    Sentences are delimited by '.', '?' or '!'.

    For example:
    >>> is_bored("Hello world")
    0
    >>> is_bored("The sky is blue. The sun is shining. I love this weather")
    1
    """

cat > solution.py <<'PY'

def is_bored(S):
    """
    You'll be given a string of words, and your task is to count the number
    of boredoms. A boredom is a sentence that starts with the word "I".
    Sentences are delimited by '.', '?' or '!'.

    For example:
    >>> is_bored("Hello world")
    0
    >>> is_bored("The sky is blue. The sun is shining. I love this weather")
    1
    """

    sentences = map(lambda x: x.strip(), ((S.replace("?", ".")).replace("!", ".")).split("."))
    return len([s for s in sentences if s.startswith("I ")])

PY


Complete the Python function and make the tests pass.

def any_int(x, y, z):
    '''
    Create a function that takes 3 numbers.
    Returns true if one of the numbers is equal to the sum of the other two, and all numbers are integers.
    Returns false in any other cases.

    Examples
    any_int(5, 2, 7) ➞ True

    any_int(3, 2, 2) ➞ False

    any_int(3, -2, 1) ➞ True

    any_int(3.6, -2.2, 2) ➞ False

    '''

cat > solution.py <<'PY'

def any_int(x, y, z):
    '''
    Create a function that takes 3 numbers.
    Returns true if one of the numbers is equal to the sum of the other two, and all numbers are integers.
    Returns false in any other cases.

    Examples
    any_int(5, 2, 7) ➞ True

    any_int(3, 2, 2) ➞ False

    any_int(3, -2, 1) ➞ True

    any_int(3.6, -2.2, 2) ➞ False

    '''

    if type(x) != int or type(y) != int or type(z) != int: return False
    return x == y + z or y == x + z or z == y + x

PY


Complete the Python function and make the tests pass.

def encode(message):
    """
    Write a function that takes a message, and encodes in such a
    way that it swaps case of all letters, replaces all vowels in
    the message with the letter that appears 2 places ahead of that
    vowel in the english alphabet.
    Assume only letters.

    Examples:
    >>> encode('test')
    'TGST'
    >>> encode('This is a message')
    'tHKS KS C MGSSCGG'
    """

cat > solution.py <<'PY'

def encode(message):
    """
    Write a function that takes a message, and encodes in such a
    way that it swaps case of all letters, replaces all vowels in
    the message with the letter that appears 2 places ahead of that
    vowel in the english alphabet.
    Assume only letters.

    Examples:
    >>> encode('test')
    'TGST'
    >>> encode('This is a message')
    'tHKS KS C MGSSCGG'
    """

    def switch_case(ch):
        if ord("A") <= ord(ch) <= ord("Z"):
            return chr(ord(ch) + 32)
        elif ord("a") <= ord(ch) <= ord("z"):
            return chr(ord(ch) - 32)
        else:
            return ch

    def vowel_change(ch):
        return ch if ch not in "aeiouAEIOU" else chr(ord(ch) + 2)

    m = "".join(map(switch_case, message))
    return "".join(map(vowel_change, m))

PY


Complete the Python function and make the tests pass.

def skjkasdkd(lst):
    """You are given a list of integers.
    You need to find the largest prime value and return the sum of its digits.

    Examples:
    For lst = [0,3,2,1,3,5,7,4,5,5,5,2,181,32,4,32,3,2,32,324,4,3] the output should be 10
    For lst = [1,0,1,8,2,4597,2,1,3,40,1,2,1,2,4,2,5,1] the output should be 25
    For lst = [1,3,1,32,5107,34,83278,109,163,23,2323,32,30,1,9,3] the output should be 13
    For lst = [0,724,32,71,99,32,6,0,5,91,83,0,5,6] the output should be 11
    For lst = [0,81,12,3,1,21] the output should be 3
    For lst = [0,8,1,2,1,7] the output should be 7
    """

cat > solution.py <<'PY'

def skjkasdkd(lst):
    """You are given a list of integers.
    You need to find the largest prime value and return the sum of its digits.

    Examples:
    For lst = [0,3,2,1,3,5,7,4,5,5,5,2,181,32,4,32,3,2,32,324,4,3] the output should be 10
    For lst = [1,0,1,8,2,4597,2,1,3,40,1,2,1,2,4,2,5,1] the output should be 25
    For lst = [1,3,1,32,5107,34,83278,109,163,23,2323,32,30,1,9,3] the output should be 13
    For lst = [0,724,32,71,99,32,6,0,5,91,83,0,5,6] the output should be 11
    For lst = [0,81,12,3,1,21] the output should be 3
    For lst = [0,8,1,2,1,7] the output should be 7
    """

    def is_prime(a):
        return not (a < 2 or any(a % x == 0 for x in range(2, int(a ** 0.5) + 1)))
    sorted_list = sorted(lst)[::-1]
    for x in sorted_list:
        if is_prime(x):
            return sum(map(lambda ch: int(ch), str(x)))

PY


Complete the Python function and make the tests pass.

def check_dict_case(dict):
    """
    Given a dictionary, return True if all keys are strings in lower
    case or all keys are strings in upper case, else return False.
    The function should return False is the given dictionary is empty.
    Examples:
    check_dict_case({"a":"apple", "b":"banana"}) should return True.
    check_dict_case({"a":"apple", "A":"banana", "B":"banana"}) should return False.
    check_dict_case({"a":"apple", 8:"banana", "a":"apple"}) should return False.
    check_dict_case({"Name":"John", "Age":"36", "City":"Houston"}) should return False.
    check_dict_case({"STATE":"NC", "ZIP":"12345" }) should return True.
    """

cat > solution.py <<'PY'

def check_dict_case(dict):
    """
    Given a dictionary, return True if all keys are strings in lower
    case or all keys are strings in upper case, else return False.
    The function should return False is the given dictionary is empty.
    Examples:
    check_dict_case({"a":"apple", "b":"banana"}) should return True.
    check_dict_case({"a":"apple", "A":"banana", "B":"banana"}) should return False.
    check_dict_case({"a":"apple", 8:"banana", "a":"apple"}) should return False.
    check_dict_case({"Name":"John", "Age":"36", "City":"Houston"}) should return False.
    check_dict_case({"STATE":"NC", "ZIP":"12345" }) should return True.
    """

    keys = list(dict.keys())
    if keys == []: return False
    lower, upper = True, True
    for k in keys:
        if type(k) != str:
            lower = upper = False
            break
        if not k.islower(): lower = False
        if not k.isupper(): upper = False
    return lower or upper

PY


Complete the Python function and make the tests pass.

def count_up_to(n):
    """Implement a function that takes an non-negative integer and returns an array of the first n
    integers that are prime numbers and less than n.
    for example:
    count_up_to(5) => [2,3]
    count_up_to(11) => [2,3,5,7]
    count_up_to(0) => []
    count_up_to(20) => [2,3,5,7,11,13,17,19]
    count_up_to(1) => []
    count_up_to(18) => [2,3,5,7,11,13,17]
    """

cat > solution.py <<'PY'

def count_up_to(n):
    """Implement a function that takes an non-negative integer and returns an array of the first n
    integers that are prime numbers and less than n.
    for example:
    count_up_to(5) => [2,3]
    count_up_to(11) => [2,3,5,7]
    count_up_to(0) => []
    count_up_to(20) => [2,3,5,7,11,13,17,19]
    count_up_to(1) => []
    count_up_to(18) => [2,3,5,7,11,13,17]
    """

    ans = []
    isprime = [True] * (n + 1)
    for i in range(2, n):
        if isprime[i]:
            ans.append(i)
            for j in range(i + i, n, i):
                isprime[j] = False
    return ans

PY


Complete the Python function and make the tests pass.

def multiply(a, b):
    """Complete the function that takes two integers and returns
    the product of their unit digits.
    Assume the input is always valid.
    Examples:
    multiply(148, 412) should return 16.
    multiply(19, 28) should return 72.
    multiply(2020, 1851) should return 0.
    multiply(14,-15) should return 20.
    """

cat > solution.py <<'PY'

def multiply(a, b):
    """Complete the function that takes two integers and returns
    the product of their unit digits.
    Assume the input is always valid.
    Examples:
    multiply(148, 412) should return 16.
    multiply(19, 28) should return 72.
    multiply(2020, 1851) should return 0.
    multiply(14,-15) should return 20.
    """

    return int(str(a)[-1]) * int(str(b)[-1])

PY


Complete the Python function and make the tests pass.

def count_upper(s):
    """
    Given a string s, count the number of uppercase vowels in even indices.

    For example:
    count_upper('aBCdEf') returns 1
    count_upper('abcdefg') returns 0
    count_upper('dBBE') returns 0
    """

cat > solution.py <<'PY'

def count_upper(s):
    """
    Given a string s, count the number of uppercase vowels in even indices.

    For example:
    count_upper('aBCdEf') returns 1
    count_upper('abcdefg') returns 0
    count_upper('dBBE') returns 0
    """

    cnt = 0
    for i in range(0, len(s), 2):
        if s[i] in "AEIOU":
            cnt += 1
    return cnt

PY