Compilare: user.cpp: In function ‘void dfs_early(int)’: user.cpp:25:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<g[node].size();i++) ^ user.cpp: In function ‘void dfs_late(int)’: user.cpp:37:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<g[node].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:49:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pm.in","r",stdin); ^ user.cpp:50:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pm.out","w",stdout); ^ user.cpp:52:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ user.cpp:54:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&v[i]); ^ user.cpp:57:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&k); ^ user.cpp:60:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&x); ^