View Compilation Error

0_0_39138552_11424.cpp: In function 'int main()':
0_0_39138552_11424.cpp:31:32: error: 'q' was not declared in this scope
   31 |             if (chu[i] == 0) { q.push(i); }
      |                                ^
0_0_39138552_11424.cpp:33:13: error: 'q' was not declared in this scope
   33 |         if (q.empty()) { ret = 1; }
      |             ^
0_0_39138552_11424.cpp:34:17: error: 'q' was not declared in this scope
   34 |         while (!q.empty()) {
      |                 ^