Compilare: user.cpp: In function ‘int main()’: user.cpp:29:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (q.size() < n) ~~~~~~~~~^~~ user.cpp:34:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<arcs[x].size(); ++i) ~^~~~~~~~~~~~~~~ user.cpp:9:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sortaret.in", "r", stdin); ^ user.cpp:10:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sortaret.out", "w", stdout); ^ user.cpp:13:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:20:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^