Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:13:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0; j<v[a].size(); j++) ^ user.cpp: In function ‘int main()’: user.cpp:24:33: 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:25:35: 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); ^ user.cpp:28:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d %d",&n,&m); ^ user.cpp:33:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d %d",&x,&y); ^