双向链表 - 数据结构

双向链表就是在单项链表的基础上增加了一个前向指针域。基本操作还是一样的，该双向链表是带有头节点的，最后一个节点的next指针域是为空的，不是指向首节点的。

双向链表的结构定义

typedef char datatype;typedef struct node{    datatype data;    struct node *prior, *next;}linknode;typedef linknode *linklist;

创建一个链表

linklist CreatDlist(void){    char ch;    linklist head;    linknode *p, *h, *r;    head = (linknode *)malloc(sizeof(linknode));    head->next = NULL;    h = head;    r = head;    while((ch = getchar()) != '\n')    {        p = (linknode *)malloc(sizeof(linknode));        p->data = ch;        p->next = NULL;        if(r == head)        {            r->next = p;        }        else        {            r->next = p;            r->prior = h;            h = h->next;        }        r = p;    }    return head;}

找到链表中一个节点

linknode * GetNode(linklist head, int i){    linknode *p = head;    int j = 0;    while(p && j<i)    {        p = p->next;        j++;    }    return p;}

插入一个节点

void InsetDlist(linklist head, datatype ch, int i){    linknode *p = head->next, *t;    int j = 0;    while(p && j < i-1)    {        p = p->next;        j++;    }    t = (linknode *)malloc(sizeof(linknode));    t->data = ch;    t->prior = p;    t->next = p->next;    p->next = t;    t->next->prior = t;}

删除一个节点

void DeleteDlist(linklist head, int i){    linknode *p = head->next;    int j = 0;    while(p && j < i-1)    {        p = p->next;        j++;    }    p->next->prior = p->prior;    p->prior->next = p->next;    puts("a");    free(p);}

显示整个双向链表

void ShowDlist(linklist head){    linknode *p = head;    while(p)    {        printf("%c", p->data);        p = p->next;    }    putchar('\n');}

释放整个双向链表

void FreeDlist(linklist head){    linknode *p;    int i = 0;    p = head;    while(p)    {        free(p);        head = head->next;        p = head;        i++;    }    printf("\nthe dlist free is ok.the node has %d.\n", i);}

双向链表的测试程序

#include <stdio.h>#include <stdlib.h>#include "dlist.h"void show(linknode *p){    printf("p->prior:%c\n", p->prior->data);    printf("p->data:%c\n", p->data);    printf("p->next:%c\n", p->next->data);}int main(void){    linklist head;    //linknode *p;    head = CreatDlist();    ShowDlist(head->next);    p = GetNode(head, 3);    show(p);    DeleteDlist(head, 3);    p = GetNode(head, 3);    show(p);    InsetDlist(head, 'x', 2);    ShowDlist(head->next);    FreeDlist(head);    return 0;}