Compilare: user.cpp: In function ‘bool verf(int, int)’: user.cpp:18:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<G[nod].size();++i) ^ user.cpp: In function ‘int main()’: user.cpp:38:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<G[x].size();++i) ^ user.cpp:46:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(G[i].size()<N-1){ ^ user.cpp:25:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("fof.in","r",stdin); ^ user.cpp:26:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("fof.out","w",stdout); ^ user.cpp:27:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&N,&M); ^ user.cpp:29:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&x,&y); ^