Compilare: user.cpp: In function ‘void back(int)’: user.cpp:23:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<G[i].size();j++) ^ user.cpp:28:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<G[i].size();j++) ^ user.cpp: In function ‘int main()’: user.cpp:39:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("metrou2.in","r",stdin); ^ user.cpp:40:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("metrou2.out","w",stdout); ^ user.cpp:42:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:44:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&cost[i]); ^ user.cpp:48:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&a,&b); ^