foo.cc:12:1: error: 'queue' does not name a type
   12 | queue<int> q;
      | ^~~~~
foo.cc: In function 'int bfs()':
foo.cc:16:16: error: 'q' was not declared in this scope
   16 |         while(!q.empty())
      |                ^
foo.cc: In function 'int main()':
foo.cc:57:17: error: 'q' was not declared in this scope
   57 |                 q.push(f[i]);
      |                 ^
foo.cc: In function 'int bfs()':
foo.cc:45:1: warning: control reaches end of non-void function [-Wreturn-type]
   45 | }
      | ^

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