C++ 代码

#include<bits/stdc++.h>
using namespace std;

int main(){
    int n;
    cin>>n;
    string s;
    cin>>s;
    deque<char> pipe;
    bool flag=n%2==0? true:false;
    for (auto& ch:s){
        if (flag) pipe.push_front(ch);
        else pipe.push_back(ch);
        flag=!flag;
    }
    cout<<string(pipe.begin(),pipe.end())<<endl;
}