How should I practice Count Index Pairs with Equal Value Offset?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Google onsite interview problems in FastPrep.

Is Count Index Pairs with Equal Value Offset associated with Google?

FastPrep tags this as a Google onsite interview coding practice problem when the problem catalog has that company and stage context.

Count Index Pairs with Equal Value Offset

Google● EasyINTERNONSITE INTERVIEW

Learn

Problem statement

Given an integer array arr, return the number of index pairs (i, j) such that 0 <= i < j < arr.length and arr[i] - arr[j] = i - j.

Function

countMatchingIndexPairs(arr: int[]) → long

Examples

Example 1

arr = [4,1,2,3]return = 3

The valid pairs are (1,2), (1,3), and (2,3).

Example 2

arr = [1,5,6]return = 1

Only indices 1 and 2 satisfy the equation.

Example 3

arr = [0,1,2,3]return = 6

Every pair satisfies the equation because arr[i] - i is always zero.

Constraints

0 <= arr.length <= 200000.
-1000000000 <= arr[i] <= 1000000000.