Compilare: user.cpp: In function ‘void dfs1(int)’: user.cpp:16:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < g[u].size(); i++) ~~^~~~~~~~~~~~~ user.cpp: In function ‘void dfs2(int)’: user.cpp:26:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < gt[u].size(); i++) ~~^~~~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:54:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < ans.size(); i++) ~~^~~~~~~~~~~~ user.cpp:56:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < ans[i].size(); j++) ~~^~~~~~~~~~~~~~~ user.cpp:34:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ctc.in", "r", stdin); ^ user.cpp:35:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ctc.out", "w", stdout); ^ user.cpp:37:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:40:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &u, &v); ^