View Compilation Error

0_0_38656319_1376.cpp: In function 'bool dfs(int)':
0_0_38656319_1376.cpp:14:12: error: 'q' was not declared in this scope
  for(int y:q[x]) if(!dfs(y)) return 0;
            ^
0_0_38656319_1376.cpp: In function 'int main()':
0_0_38656319_1376.cpp:37:4: error: 'q' was not declared in this scope
    q[a].emplace_back(b^1);
    ^