双循环链表

#include<bits/stdc++.h>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <vector>


using namespace std;

typedef int ElemType;
typedef struct node
{
	ElemType data;
	struct node*pre;
	struct node*next;
}linkNode,*linkList;

//链表初始化
linkList initLinkList()
{
    linkList head=(linkList)malloc(sizeof(linkNode));
    if(!head)
    {
        printf("动态内存分配失败!\n");
        exit(0);
    }
    head->next=head;
    head->pre=head;

    printf("链表初始化成功!\n");
    return head;
}

//建立结点 
linkList createNode(int val)
{
	linkList head=(linkList)malloc(sizeof(linkNode));
	head->data = val;
	head->pre = nullptr;
	head->next = nullptr;
	return head;
}

//尾插法 
void insertLinkListByNext(linkList l,int x)
{
	linkList newNode = createNode(x);
	linkList lastNode = l;
	while(lastNode->next != l)
	{
		lastNode = lastNode->next;
	}
	l->pre = newNode;
	newNode->next = l;
	lastNode->next = newNode;
	newNode->pre = lastNode;
}


//头插法
void insertNodeByHead(linkList headNode,int data)
{
	linkList newNode = createNode(data);
	newNode->pre = headNode;
	newNode->next = headNode->next;
	headNode->next->pre = newNode;
	headNode->next = newNode;
}


 
//正序输出 
void printList(linkList l)
{
	linkList p = l->next;
	while(p != l)
	{
		printf("%d",p->data);
		p = p->next;	
	}	
	printf("\n");
} 

//逆序输出
void printList_reverse(linkList l)
{
	linkList p = l->pre;
	while(p != l)
	{
		printf("%d",p->data);
		p = p->pre;	
	}	
	printf("\n");
} 

//查找指定元素
void searchElement(linkList l,int x)
{
	linkList posNode = l->next;
	linkList posNodeprior = l;
	while(posNode->data != x)
	{
		posNodeprior = posNode;
		posNode = posNodeprior->next;
		if(posNode == l)
		{
			printf("不存在元素!\n");
			return ;	
		} 
	}
	printf("该元素存在!\n");
}  

//查找指定元素并更改
void modifyElement(linkList l,int x,int elem)
{
	linkList posNode = l->next;
	linkList posNodeprior = l;
	while(posNode->data != x)
	{
		posNodeprior = posNode;
		posNode = posNodeprior->next;
		if(posNode  == l)
		{
			printf("不存在元素！\n");
		}
	}
	posNode->data = elem;
	printf("修改成功!\n");
}   


//删除指定元素
void Specify(linkList headNode,int posData) 
{
	linkList posNode = headNode->next;
	linkList posNodeprior = headNode;
	
	while(posNode->data != posData)
	{
		posNodeprior = posNode;
		posNode = posNodeprior->next;	
		if(posNode == headNode)
		{
			printf("不存在指定位置，无法删除！\n");
			return;
		}
	}	
	posNodeprior->next = posNode->next;
	posNode->next->pre = posNodeprior;
	free(posNode);
}

int main()
{
	linkList head = initLinkList();
	insertLinkListByNext(head,1);
	insertLinkListByNext(head,2);
	insertLinkListByNext(head,4);
	insertLinkListByNext(head,3);
	insertLinkListByNext(head,5);
	searchElement(head,0);
	printList(head);
	printList_reverse(head);
	
	
	linkList head2 = initLinkList();
	insertNodeByHead(head2,7);
	insertNodeByHead(head2,8);
	insertNodeByHead(head2,9);
	printList(head2);
	printList_reverse(head2);
	
	
	return 0;
}