Compilare: user.cpp: In function ‘void BFS()’: user.cpp:24:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < a[x+1].size(); ++i) ^ user.cpp:35:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < b[x].size(); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:48:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pcb.in","r",stdin); ^ user.cpp:49:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pcb.out","w",stdout); ^ user.cpp:53:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d",&N,&M,&f); ^ user.cpp:56:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&x,&y); ^