Welcome to Subscribe On Youtube
Formatted question description: https://leetcode.ca/all/2176.html
2176. Count Equal and Divisible Pairs in an Array (Easy)
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.
Constraints:
1 <= nums.length <= 1001 <= nums[i], k <= 100
Similar Questions:
Solution 1. Brute Force
// OJ: https://leetcode.com/problems/count-equal-and-divisible-pairs-in-an-array/
// Time: O(N^2)
// Space: O(1)
class Solution {
public:
int countPairs(vector<int>& A, int k) {
int N = A.size(), ans = 0;
for (int i = 0; i < N; ++i) {
for (int j = i + 1; j < N; ++j) {
ans += A[i] == A[j] && i * j % k == 0;
}
}
return ans;
}
};