Leetcode 2176. Count Equal and Divisible Pairs in an Array

Count the number of index pairs (i < j) where the elements are equal and the product i * j is divisible by k — the core challenge is combining value equality grouping with a divisibility condition on indices. With n ≤ 100 you can group indices by value and count qualifying index pairs per group (brute-force O(n^2) is sufficient).