s->next = p;
s->prior = p->prior;
p->prior->next = s;
p->prior = s;

p->prior->next = p->next;
p->next->prior = p->prior;
delete p;

#include<iostream>
#include<cstddef>
#include<cstdio>
using namespace std;

const int OK = 1;
const int ERROR = 0;
const int LETTERNUM = 26;
typedef char ElemType;

struct Node{
  ElemType data;
  Node * prior;//前驅(qū)結(jié)點
  Node * next;//后驅(qū)結(jié)點 
};

int InitList(Node *&L){
  Node *p,*q;
  int i;
  
  L = new Node; //頭結(jié)點 
  L->next = L->prior = NULL;
  p = L; //p是當前指針
   
  for(int i=0;i<LETTERNUM;i++){
    q = new Node; //q是臨時指針 
    q->data = 'A' + i;
    q->prior = p;
    q->next = p->next;
    p->next = q;
    p = q;//指針移動 
  }
  p->next = L->next; //尾結(jié)點指向head->next(第一個有字母的地址) 
  L->next->prior = p;
  
  return OK;
}

void Change(Node *&L,int i){ //移動頭指針 
  if (i>0){
    while(i--){
      L = L->next;
    }
  }
  else if (i<0){
    L = L->next ; 
    while(i++){
      L = L->prior;
    }
  }
  else{
    L = L->next;
  }
}


int main(){
  Node *head = NULL;
  int i,n;
  InitList(head);
  //Node *s_head = head; // 保存頭結(jié)點之后刪除 
  cout<<"輸入位置："<<endl;
  cin>>n;
  Change(head,n);
  
  for(i = 0;i<LETTERNUM;++i){
    head = head->next;
    cout<<head->data<<" "; 
  }
  
  cout<<endl;
  return 0;
}