Compilare: user.cpp: In function ‘void bfs()’: user.cpp:22:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<graph[n].size(); ++i) { ^ user.cpp: In function ‘int main()’: user.cpp:33:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bfs.in", "r", stdin); ^ user.cpp:34:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bfs.out", "w", stdin); ^ user.cpp:37:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &N, &M, &S); ^ user.cpp:39:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &x, &y); ^