func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     vector<vector<int>> v(n);     int mat[4][4] = {         {8, 9, 1, 13}, {3, 12, 7, 5}, {0, 2, 4, 11}, {6, 10, 15, 14}};     int ans[n][n];     for (int i = 0; i < n * n; i++) {       int x = i / n;       v[x].push_back(i);     }     int count = 0;     for (int i = 0; i < n; i += 4) {       for (int j = 0; j < n; j += 4) {         for (int k = i; k < i + 4; k++) {           for (int l = j; l < j + 4; l++) {             ans[k][l] = count++;           }         }       }     }     for (int i = 0; i < n; i++) {       for (int j = 0; j < n; j++) {         if (j == 0)           cout << ans[i][j];         else           cout <<     << ans[i][j];       }       cout << endl;     }     return 0;   }   