Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:14:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<v[n].size(); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:25:29: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dfs.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("dfs.out","w",stdout); ^