View Compilation Error

0_0_17088060_25388.cpp: In function 'int bfs(int, int, int, int)':
0_0_17088060_25388.cpp:46:5: error: 'queue' was not declared in this scope
     queue<int> a,b;
     ^
0_0_17088060_25388.cpp:46:11: error: expected primary-expression before 'int'
     queue<int> a,b;
           ^
0_0_17088060_25388.cpp:50:5: error: 'a' was not declared in this scope
     a.push(x);
     ^
0_0_17088060_25388.cpp:51:5: error: 'b' was not declared in this scope
     b.push(y);
     ^
0_0_17088060_25388.cpp:59:35: error: 'ny' was not declared in this scope
             int dx=nx+dr[i][0],dy=ny+dr[i][1];
                                   ^