Compilare: user.cpp: In function ‘void back(int, int)’: user.cpp:15:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<graph[pos].size();++i)ok[graph[pos][i]]++; ^ user.cpp:17:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<graph[pos].size();++i)ok[graph[pos][i]]--; ^ user.cpp: In function ‘int main()’: user.cpp:23:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("alianta.in","r",stdin); ^ user.cpp:24:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("alianta.out","w",stdout); ^ user.cpp:25:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&T); ^ user.cpp:28:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:34:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&a,&b); ^