View Compilation Error

0_0_4793842_5396.cpp: In function `int main()':
0_0_4793842_5396.cpp:84: error: `dfs' undeclared (first use this function)
0_0_4793842_5396.cpp:84: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_4793842_5396.cpp:85: error: `check' undeclared (first use this function)