Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:31:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int d=1;d<sons.size();d++) ^ user.cpp:32:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<sons.size();i++) ^ user.cpp:35:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(j==sons.size()) ^ user.cpp: In function ‘int main()’: user.cpp:53:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("petsoft.in","r",stdin); ^ user.cpp:54:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("petsoft.out","w",stdout); ^ user.cpp:55:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ user.cpp:58:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] v[x].push_back(i); ^