Count pairs Sum in matrices

// { Driver Code Starts
#include <bits/stdc++.h>
using namespace std;



 // } Driver Code Ends


//User function template for C++
class Solution{
public:	
	
	int countPairs(vector<vector<int>> &mat1, vector<vector<int>> &mat2, int n, int x)
	{
	    int count = 0; 
  
    // unordered_set 'us' implemented as hash table 
    unordered_set<int> us; 
  
    // insert all the elements of mat2[][] in 'us' 
    for (int i = 0; i < n; i++) 
        for (int j = 0; j < n; j++) 
            us.insert(mat2[i][j]); 
  
    // for each element of mat1[][] 
    for (int i = 0; i < n; i++) 
        for (int j = 0; j < n; j++) 
  
            // if (x-mat1[i][j]) is in 'us' 
            if (us.find(x - mat1[i][j]) != us.end()) 
                count++; 
  
    // required count of pairs 
    return count; 
	}
};

// { Driver Code Starts.


int main() 
{

   	ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);
   
   	int t;
    cin >> t;
    while (t--)
    {
        int n, x;
        cin >> n >> x;

        vector<vector<int>> mat1(n, vector<int>(n, -1));
        vector<vector<int>> mat2(n, vector<int>(n, -1));

        for(int i = 0; i < n; i++)
        {
        	for(int j = 0; j < n; j++)
        	{
        		cin >> mat1[i][j];
        	}
        }

        for(int i = 0; i < n; i++)
        {
        	for(int j = 0; j < n; j++)
        	{
        		cin >> mat2[i][j];
        	}
        }

        Solution ob;

        cout << ob.countPairs(mat1, mat2, n, x) << "\n";

    }

    return 0;
}  // } Driver Code Ends