> #include<iostream>
> #include<vector>
> #include<string>
> #include<algorithm>
> using namespace std;
> 
> int main ()
> {
> 	vector<string>vect;
> 	string tem;
> 	int len;
> 	cin>>len;
> 	int count=0;
> 	int i;
> 	vector<string>::iterator beg;
> 	vector<string>::iterator end;
> 	for(i=0;i<len;i++)
> 	{
> 		cin>>tem;
> 		vect.push_back(tem);
> 	}
> 
> 	while(!vect.empty())
> 	{
> 
> 		if(*vect.begin()<*(vect.end()-1))
> 		{
> 			cout<<*(vect.begin());
> 			vect.erase(vect.begin());
> 			++count;
> 			if(count%80==0)
> 				cout<<endl;
> 			continue;
> 		}
> 
> 		if(*vect.begin()>*(vect.end()-1))
> 		{
> 			cout<<*(vect.end()-1);
> 			vect.erase(vect.end()-1);
> 			++count;
> 			if(count%80==0)
> 				cout<<endl;
> 			continue;
> 
> 
> 		}
> 		if(*vect.begin()==*(vect.end()-1))
> 		{
> 
> 			beg=vect.begin ();
> 			end=vect.end()-1;
> 			for(i=0;;i++)
> 			{
> 				++beg;
> 				--end;
> 				if(beg>=end)
> 				{
> 					cout<<*vect.begin();
> 					vect.erase(vect.begin());
> 					++count;
> 					break;
> 				}
> 
> 
> 
> 				if(*beg<*end&&beg<end)
> 				{
> 					cout<<*vect.begin();
> 					vect.erase(vect.begin());
> 					++count;
> 					break;
> 				}
> 				if(*beg>*end&&beg<end)
> 				{
> 					cout<<*(vect.end()-1);
> 					vect.erase(vect.end()-1);
> 					++count;
> 					break;
> 				}
> 				if(*beg==*end&&beg<end)
> 				{
> 					continue;
> 
> 				}
> 			}
> 		}
> 		if(count%80==0)
> 			cout<<endl;
> 	}
> 	return 0;
> }
> 
> 虽然我还没有写出来，但是感觉用stl有点把简单问题复杂化
> 
> 
>