Compilare: user.cpp: In function ‘int main()’: user.cpp:28:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<vecin[i].size();j++) ^ user.cpp:9:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("itree.in","r",stdin); ^ user.cpp:10:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("itree.out","w",stdout); ^ user.cpp:13:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d",&t); ^ user.cpp:15:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d",&n); ^ user.cpp:18:33: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d%d",&x,&y); ^ user.cpp:37:9: warning: ‘cnt’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (cnt<=2) printf ("YES\n"); ^