Count Equal and Divisible Pairs in an Array

给一个数组, 求一个pair, nums[i] == nums[j] 并且 i * j 能被k整除.

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