HDU 1276 士兵队列训练问题

#include"iostream"
#include"list"
using namespace std;
int main()
{
	int T;
	cin>>T;
	while(T--)
	{
		int n;
		cin>>n;
        list<int> s;
        if(n==0) cout<<0<<endl;
        else
        {
        for(int i=1;i<=n;i++)
			s.push_back(i);
        //cout<<s.size()<<endl;
		list<int>::iterator it,ip;
		int f=1;
		int flag=s.size();
		while(flag>3)
		{
            for(it=s.begin();it!=s.end();)
			{
             if(f==2)
			 {
			   f=1;
			   ip=it;
			   it++;
             s.erase(ip);
             flag--;
			 }
			 else
			 {
               f++;
               it++;
			 }
			}
			f=1;if(flag<=3) break;
            if(flag<=3) break;
			for(it=s.begin();it!=s.end();)
			{
             if(f==3)
			 {
			   f=1;
			   ip=it;
			   it++;
             s.erase(ip);
             flag--;
			 }
			 else
			 {
               f++;
               it++;
			 }
			}

			f=1;if(flag<=3) break;
		}
		int ff=0;
     for(it=s.begin();it!=s.end();++it)
	   {
	         cout<<(*it);
	         ff++;
	         if(ff<=flag-1) cout<<‘ ‘;
	   }
	   cout<<endl;
        }
    }
return 0;
}