View Compilation Error

0_0_11517704_12670.cpp: In function `bool spfa(int)':
0_0_11517704_12670.cpp:14: error: `n' undeclared (first use this function)
0_0_11517704_12670.cpp:14: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_11517704_12670.cpp: In function `int main()':
0_0_11517704_12670.cpp:68: error: `flag' undeclared (first use this function)
0_0_11517704_12670.cpp:74: error: `dfs' undeclared (first use this function)