hacker.cpp: In function 'void compute(int)': hacker.cpp:20: warning: statement has no effect hacker.cpp: In function 'void downDFS(int, int)': hacker.cpp:33: warning: comparison between signed and unsigned integer expressions hacker.cpp: In function 'void upDFS(int, int)': hacker.cpp:52: warning: comparison between signed and unsigned integer expressions hacker.cpp:68: warning: comparison between signed and unsigned integer expressions hacker.cpp: In function 'void dadDFS(int, int)': hacker.cpp:87: warning: comparison between signed and unsigned integer expressions hacker.cpp: In function 'int main()': hacker.cpp:120: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result hacker.cpp:121: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result hacker.cpp:123: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result hacker.cpp:125: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result hacker.cpp:138: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result hacker.cpp: In function 'void upDFS(int, int)': hacker.cpp:47: warning: 'node1' may be used uninitialized in this function hacker.cpp:47: warning: 'node2' may be used uninitialized in this function