Find the number of ways to select two pairs that match the condition above. Two ways are considered different if they consist of different pairs. code example

Example: two elements with difference K in c++

bool diffK(int A[], int N, int K) {
    sort(A, A+N);
    int i = 0, j = 0;
    while (i < N && j < N) {
        if (A[i] == A[j] + K) return true;
        else if (A[i] < A[j] + K) i++;
        else j++;
    }
    return false;
}