View Compilation Error

0_0_10811631_11446.cpp: In function `void dijkstra()':
0_0_10811631_11446.cpp:20: error: `f' undeclared (first use this function)
0_0_10811631_11446.cpp:20: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_10811631_11446.cpp:21: error: expected `;' before "return"