View Compilation Error

0_0_26800838_31162.cpp: In function 'bool spfa(int&, double&)':
0_0_26800838_31162.cpp:57:2: error: 'queue' was not declared in this scope
  queue<int> Q;
  ^
0_0_26800838_31162.cpp:57:8: error: expected primary-expression before 'int'
  queue<int> Q;
        ^