双链表练习--交换节点

建立一个双链表，设计一个算法查找第一个元素值为5的节点，将其与后继结点进行交换。

#include <iostream.h>
#include <stdio.h>
#define M 5

typedef struct DLinkList{
	int x;//data x;
	struct DLinkList *next;//pointing to the next DLinkList;
	struct DLinkList *prior;//pointing to the prior DLinkList;
}DLinkList;
void main(){
    //set an empty link;
	DLinkList *head,*pr;
	head=new DLinkList;
    head->next=head;
	head->next=head;
    pr=head;//pr points to the last node; 
	//seting a link with m nodes;
	for(int i=1;i<=M;i++){
	    DLinkList *p=new DLinkList;//creat a new node;
		cin>>p->x;//Do input 5 only once;
		pr->next=p;//let the last node's  next point to p;
		p->prior=pr;//let the newly-created node's prior point to the last node;
		p->next=head;//let the newly-created node's next point to the head node;
		head->prior=p;//let the head node 's prior point to the created node；
		pr=p;//let pr point to the newly-created node;
	}
   //finding the node with x=5;
   pr=head;
   while(pr->x!=5){
	   pr=pr->next;
   }
   //exchanging *pr for the node after *pr;
   DLinkList *ps=pr->next;//creating a point ps pointing to the one after *pr
   DLinkList *pt=ps->next;//creating a point pt pointing to the one after *ps
   pr->prior->next=ps;//let the node before *pr's next point to *ps;
   ps->prior=pr->prior;//let *ps's prior point to the node before *pr;
   ps->next=pr;//let *ps's next point to the node  *pr
   pr->prior=ps;//let *pr'prior point to *ps; 
   pr->next=pt;//let *pr's next point to the node after *ps;
   pt->prior=pr;//let the node after *ps point to *pr;
   pr=head->next;//pr points to the node with data;
   while(pr!=head){//one circle
	   cout<<pr->x<<" ";
	   pr=pr->next;
   }
   cout<<endl;//
}