Compilare: user.cpp: In function ‘int main()’: user.cpp:36:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("spider.in","r",stdin); ^ user.cpp:37:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("spider.out","w",stdout); ^ user.cpp:38:15: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ user.cpp:39:15: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&m); ^ user.cpp:42:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&a[i][j]); ^ user.cpp:58:11: warning: ‘y’ may be used uninitialized in this function [-Wmaybe-uninitialized] vc[cate]=y; ^ user.cpp:57:12: warning: ‘x’ may be used uninitialized in this function [-Wmaybe-uninitialized] v[++cate]=x; ^