View Compilation Error

0_0_4456479_1776.cpp: In function `void bfs()':
0_0_4456479_1776.cpp:60: error: `priority_queue' undeclared (first use this function)
0_0_4456479_1776.cpp:60: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_4456479_1776.cpp:60: error: expected primary-expression before '>' token
0_0_4456479_1776.cpp:60: error: `Q' undeclared (first use this function)