Compilare: user.cpp: In function ‘int main()’: user.cpp:56:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<arb[nod].v1.size();j++) sol[arb[nod].v1[j]]++; ^ user.cpp:37:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("virus.in","r",stdin); ^ user.cpp:38:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("virus.out","w",stdout); ^ user.cpp:40:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n",&l,&n); ^ user.cpp:42:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(sir+1); ^ user.cpp:45:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&l1); ^ user.cpp:46:21: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(sir1+1); ^ /tmp/ccrO70u8.o: In function `main': user.cpp:(.text.startup+0xbe): warning: the `gets' function is dangerous and should not be used.