3SUM

The 3SUM problem asks if a given set of  numbers contains three elements that sum to zero.

void ThreeSum(int S [], int n)

{

    // Assumes S is sorted in increasing order

    int a, b, c, start, end;

    for (int i = 0; i <= n - 3; i++)

    {

        a = S[i];

        start = i + 1;

        end = n - 1;

        while (start < end)

        {

            b = S[start];

            c = S[end];

            if (a + b + c == 0)

            {

                std::cout << "3SUM: " << a << ", " << b << ", " << c << "\n";

                start = start + 1;

                end = end - 1;

            }

            else if (a + b + c > 0)

            {

                end = end - 1;

            }

            else

            {

                start = start + 1;

            }

        }

    }

}