wa了一个点 还在思考
用了离散化的反向操作 将有序映射成无序
需要自己先构造一个有序

 int mm = 1;
   ys[mm++] = fs[s];
    while(s!="-1"){
        s=nes[s];
        ys[mm++] = fs[s];
    }

    核心代码

#include<bits/stdc++.h>
using namespace std;
const int N = 1e5+10;
//map<string,int> idx ;
 string idx[N],ne[N];  //基本元素  当前id和下一个的id
 map<string,int> da ;//用 字符串来匹配 data
 map<string,int> fs ;//反身  idx的反身下标数组
  map<string,string> nes;   //用于找到正确的链表顺序
 int ys[N];  //映射数组 保证从有序映射到无序真实
int main()
{
    string f ,f2;
    int n;
    cin>>f>>n; string s = f;
  //  idx[1] = f;
    int id;
    for (int i = 1; i <= n; i ++ ){
        cin>>f>>id>>f2;
        idx[i] = f;
        fs[f] = i;
        da[f] = id;
        ne[i] = f2;
        nes[f] = f2;
    }
   int mm = 1;
   ys[mm++] = fs[s];
    while(s!="-1"){
        s=nes[s];
        ys[mm++] = fs[s];
    }
    int cnt = 1;
    for (int i = 1; i <= (n+1)/2; i ++ ){
         for(int j = 0;j<2;j++){
    if(n%2==1&&i==(n+1)/2) j=1;
        if(cnt%2==1){
            int j = n-i+1;
            cout<<idx[ys[j]]<<" ";
            cout<<da[idx[ys[j]]]<<" ";
             if(n%2==1&&i==(n+1)/2) cout<<-1<<endl;
             else
            cout<<idx[ys[i]]<<endl;
        }else{
               int j = n-i+1;
            cout<<idx[ys[i]]<<" ";
            cout<<da[idx[ys[i]]]<<" ";
            if(n%2==0&&n-i==n/2)
            cout<<-1<<endl;
            else
            cout<<idx[ys[n-i]]<<endl;

        }
        cnt++;
        }
    }
    //7 1 6 2 5 3 4
}

ac 代码
这个题不能把n直接当做合法链表的总数
有脏数据
所以应该用mm

#include<bits/stdc++.h>
using namespace std;
const int N = 1e5+10;
//map<string,int> idx ;
 string idx[N],ne[N];
 map<string,int> da ;
 map<string,int> fs ;
  map<string,string> nes;
 int ys[N];
int main()
{
    string f ,f2;
    int n;
    cin>>f>>n; string s = f;
  //  idx[1] = f;
    int id;
    for (int i = 1; i <= n; i ++ ){
        cin>>f>>id>>f2;
        idx[i] = f;
        fs[f] = i;
        da[f] = id;
        ne[i] = f2;
        nes[f] = f2;
    }
   int mm = 1;
   ys[mm++] = fs[s];
    while(s!="-1"){

        s=nes[s]; //cout<<s<<endl;
        ys[mm++] = fs[s];
    }
   // cout<<mm-2<<endl;
    n = mm-2;
    int cnt = 1;
    for (int i = 1; i <= (n+1)/2; i ++ ){
         for(int j = 0;j<2;j++){
    if(n%2==1&&i==(n+1)/2) j=1;
        if(cnt%2==1){
            int j = n-i+1;
            cout<<idx[ys[j]]<<" ";
            cout<<da[idx[ys[j]]]<<" ";
             if(n%2==1&&i==(n+1)/2) cout<<-1<<endl;
             else
            cout<<idx[ys[i]]<<endl;
        }else{
               int j = n-i+1;
            cout<<idx[ys[i]]<<" ";
            cout<<da[idx[ys[i]]]<<" ";
            if(n%2==0&&n-i==n/2)
            cout<<-1<<endl;
            else
            cout<<idx[ys[n-i]]<<endl;

        }
        cnt++;
        }
    }
    //7 1 6 2 5 3 4
}