Nice Pairs solution codechef

Given a string $S$ of length $N$ containing only numeric characters, find the number of Nice Pairs.

A Nice Pair is a pair of indices – $(i, j)$ such that $1 \leq i < j \leq N$ and $j - i = | S_{j} - S_{i} |$ .

First line will contain $T$ , number of testcases. Then the testcases follow.
The first line of each testcase contains a single integer, $N$ , the length of the string
The second line of each testcase contains a string $S$ of length $N$ . The string contains only numeric characters $[0 - 9]$

For each testcase, output a single integer – the number of nice pairs in the given string.

3
2
9

Test Case $1$ : There are $3$ nice pairs in the given string – $(1, 2), (1, 3), (2, 3)$

Test Case $2$ : There are $2$ nice pairs in the given string – $(2, 3), (3, 5)$

For Solution