2176.CountPairs.cs

// 2176. Count Equal and Divisible Pairs in an Array

// Given a 0-indexed integer array nums of length n and an integer k, return the number of pairs (i, j) where 0 <= i < j < n, such that nums[i] == nums[j] and (i * j) is divisible by k.

// Example 1:

// Input: nums = [3,1,2,2,2,1,3], k = 2
// Output: 4
// Explanation:
// There are 4 pairs that meet all the requirements:
// - nums[0] == nums[6], and 0 * 6 == 0, which is divisible by 2.
// - nums[2] == nums[3], and 2 * 3 == 6, which is divisible by 2.
// - nums[2] == nums[4], and 2 * 4 == 8, which is divisible by 2.
// - nums[3] == nums[4], and 3 * 4 == 12, which is divisible by 2.
// Example 2:

// Input: nums = [1,2,3,4], k = 1
// Output: 0
// Explanation: Since no value in nums is repeated, there are no pairs (i,j) that meet all the requirements.

public class Solution {
    public int CountPairs(int[] nums, int k) {
        int count = 0;
        for(int i = 0; i < nums.Length-1; i++){
            for(int j = i+1 ; j < nums.Length; j++){
                if(nums[i] == nums[j] && (i*j) % k == 0)
                    count++;
            }
        }
        return count++;
    }
}