Function pairs_with_sum

data_structures/arrays/pairs_with_given_sum.py:13–23

Return the no. of pairs with sum "sum" >>> pairs_with_sum([1, 5, 7, 1], 6) 2 >>> pairs_with_sum([1, 1, 1, 1, 1, 1, 1, 1], 2) 28 >>> pairs_with_sum([1, 7, 6, 2, 5, 4, 3, 1, 9, 8], 7) 4

(arr: list, req_sum: int)

def pairs_with_sum(arr: list, req_sum: int) -> int:
    """
    Return the no. of pairs with sum "sum"
    >>> pairs_with_sum([1, 5, 7, 1], 6)
    2
    >>> pairs_with_sum([1, 1, 1, 1, 1, 1, 1, 1], 2)
    28
    >>> pairs_with_sum([1, 7, 6, 2, 5, 4, 3, 1, 9, 8], 7)
    4
    """
    return len([1 for a, b in combinations(arr, 2) if a + b == req_sum])


if __name__ == "__main__":