Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:13:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[p].size();++i){ ~^~~~~~~~~~~~ user.cpp: In function ‘void dfs2(int)’: user.cpp:23:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<t[p].size();++i){ ~^~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:54:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<r[i].size();++j) ~^~~~~~~~~~~~ user.cpp:31:32: 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:32:34: 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:34:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&N,&M); ^ user.cpp:36:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&x,&y); ^