I saw the of ranklist Biweekly Contest 72. The contestant, with the user ID : abratan7870 has a same solution with that of : vaish05 The only difference is of a new line:
image

abratan7870's solution:

class Solution {
public:
    int countPairs(vector<int>& nums, int k) {
        int ans=0,n=nums.size();
        for(int i=0;i<n;i++)
        {
            for(int j=i+1;j<n;j++)
            {
                if(nums[i]==nums[j] && (i*j)%k==0)
                    ans++;
            }
        }
        return ans;
    }
};

vaish05's solution:

class Solution {
public:
    int countPairs(vector<int>& nums, int k) {
        int ans=0;
        for(int i=0; i<nums.size()-1; i++){
            for(int j=i+1; j<nums.size(); j++){
                if(nums[i]==nums[j] && (i*j)%k==0) ans++;
            }
        }
        return ans;
    }
};

Diff checker : https://www.diffchecker.com/V8GNOGcG
The only difference between the two solution is the use of n=nums.size() and putting the update statement(ans++) in the next line. Rest the entire solution is exact copy of the other.
The contestant happens to be ranked at 559. This is just one instance where the plag checker wasn't able to detect the cheating. Just think, how many such contestants have fooled the system till now to get good rating.

I have reported this to Leetcode, but didn;t received any response yet.

Why leetcode didn't respond to the report?
How these guys are able to fool the system?
Such malpractices really demotivate actual coders. Please take action