Compilare: main.cpp: In function 'int main()': main.cpp:32:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<arcs[x].size(); ++i) ~^~~~~~~~~~~~~~~ main.cpp:9:34: 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); ^ main.cpp:10:36: 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); ^ main.cpp:13:33: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &n, &m, &start); ^ main.cpp:23:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^