2176. Count Equal and Divisible Pairs in an Array

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problem

solution

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class Solution {
public:
    int countPairs(vector<int>& nums, int k) {
        // brute force => time complexity O(n^2)
        int n = nums.size(), count = 0;
        for(int i=0;i<n-1;++i){
            for(int j=i+1;j<n;++j){
                if(nums[i]==nums[j] && (i*j)%k==0) count++;
            }
        }
        return count;
    }
};

analysis

  • time complexity O(n)
  • speed complexity O(1)