Compilare: user.cpp: In function ‘void BFS()’: user.cpp:26:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < a[x].size(); ++i) ^ user.cpp: In function ‘void Solve()’: user.cpp:44:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 0; j < a[i].size(); ++j) ^ user.cpp: In function ‘int main()’: user.cpp:52:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("reinvent.in","r",stdin); ^ user.cpp:53:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("reinvent.out","w",stdout); ^ user.cpp:57:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d",&N,&M,&X); ^ user.cpp:60:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&x,&y); ^ user.cpp:65:46: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for(i = 1; i <= X; ++i) scanf("%d",&v[i]); ^