usrbinenv python3 given an array of integers and an integer reqsum find the number of pairs of array elements whose sum is equal to reqsum https practice geeksforgeeks orgproblemscountpairswithgivensum50220 return the no of pairs with sum sum pairswithsum1 5 7 1 6 2 pairswithsum1 1 1 1 1 1 1 1 2 28 pairswithsum1 7 6 2 5 4 3 1 9 8 7 4 usr bin env python3 given an array of integers and an integer req_sum find the number of pairs of array elements whose sum is equal to req_sum https practice geeksforgeeks org problems count pairs with given sum5022 0 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
from itertools import combinations


def pairs_with_sum(arr: list, req_sum: int) -> int:
    
    return len([1 for a, b in combinations(arr, 2) if a + b == req_sum])


if __name__ == "__main__":
    from doctest import testmod

    testmod()