Twin Pairs Problem Statement

Given an array A of size N, find the number of twin pairs in the array. A twin pair is defined as a pair of indices x and y such that x < y and A[y] - A[x] = y - x.

Input:

The first line of input contains an integer T, denoting the number of test cases.
The first line of each test case contains an integer N denoting the size of the array.
The next line contains N space-separated integers representing the array A.

Output:

For each test case, output a single integer denoting the number of twin pairs in the array.

Example:

Input:

2
5
1 2 3 4 5
4
4 3 2 1

Output:

4
0

Constraints:

• 1 <= T <= 5
• 1 <= N <= 10^5
• 1 <= A[i] <= N
• Time Limit: 1 sec

Note:

You are not required to print the expected output. It has already been taken care of. Just implement the function.