Compilare: user.cpp: In function ‘void bfs(int)’: user.cpp:23:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < adj[next.first].size(); i++){ ^ user.cpp: In function ‘int main()’: user.cpp:34:31: 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:35:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bfs.out", "w", stdout); ^ user.cpp:36:29: 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:38:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &from, &to); ^