Compilare: main.cpp: In function 'void BFS(int)': main.cpp:28:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < G[act].size(); ++i) { ~~^~~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:40:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("amici2.in","r",stdin); ^ main.cpp:41:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("amici2.out","w",stdout); ^ main.cpp:43:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&t); ^ main.cpp:46:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&n,&m); ^ main.cpp:54:29: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&a,&b); ^