Compilare: user.cpp: In function ‘void BFS(int, int)’: user.cpp:24:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < a[x].size(); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:37:11: warning: unused variable ‘j’ [-Wunused-variable] int i,j,x,y,res=0; ^ user.cpp:34:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("graf.in","r",stdin); ^ user.cpp:35:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("graf.out","w",stdout); ^ user.cpp:39:37: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d",&N,&M,&X,&Y); ^ user.cpp:42:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&x,&y); ^