DoublyLinkedList(双向链表)

　　本来还不会写双向链表的，但最近学习了二叉树后，突然意识到这不就是双向链表嘛，然后通过对二叉树的理解，实现了一下双向链表。

　　代码：

#define SIZE 10

DouLL * head, *n, *p;

head =（DouLL * )malloc(sizeof(DouLL));
p = head;　　/* p指针的作用很重要 */
p->Item = 1;
p->prev = p->next = NULL;
for (int i = 1; i < SIZE; i++)
{
	n =（DouLL * )malloc(sizeof(DouLL));
	n->Item = i + 1;
	n->prev = p;　　/* 防止找不到头结点 */
	p->next = n;
	p = p->next;
}
n->next = NULL;    /* 若要循环应改为: n -> next = head; */
head->prev = NULL; /* head -> prev = n; */

　　code:

//双向链表
#include<stdio.h>
#include<stdlib.h>
#include<conio.h>

#define bool int
#define true 1
#define false 0;

typedef struct douLinkList
{
    struct douLinkList * next;        //下一个
    struct douLinkList * prev;        //前一个
    int Item;
}DouLL;

/* 实现插入功能 */
bool InsertLL();
/* 实现删除功能 */
bool deleteLL();

bool InsertLL(DouLL * h, int X, int i)
{
    DouLL * p;
    int j;

    j = 1;
    while(j < i - 1 && h)
    {
        h = h -> next;
        ++ j;
    }
    p = malloc(sizeof(DouLL));
    p -> Item = X;
    p -> prev = h;
    p -> next = h -> next;
    h -> next -> prev = p;
    h -> next = p;
    return true;
}

bool deleteLL(DouLL * h, int X)
{
    DouLL * temp;

    if(!h)
    {
        fprintf(stderr, "链表已空!\n");
        return false;
    }
    while(X != h -> Item && h)
    {
        h = h -> next;
    }
    temp = h;
    h -> prev -> next = h -> next;
    h -> next -> prev = h -> prev;
    free(temp);
    return true;
}

int main()
{
    char c;
    int i, SIZE, X;
    DouLL * head, * n, * p;

    puts("初始链表长度:");
    scanf("%d", &SIZE);

    head = malloc(sizeof(DouLL));
    p = head;
    p -> Item = rand() % 100 + 50;
    p -> prev = p -> next = NULL;
    for(i = 1; i < SIZE; i++)
    {
        n = malloc(sizeof(DouLL));
        n -> Item = rand() % 1000 + 50;
        n -> prev = p;
        p -> next = n;
        p = p -> next;
    }
    n -> next = NULL;
    head -> prev = NULL;

    puts("1) 显示    2) 删除");
    puts("3) 插入    4) 退出");
    while(1)
    {
        c = getch();
        if(c == '1')
        {
            puts("Order:");

            p = head;
            while(p)
            {
                printf("%d ", p -> Item);
                p = p -> next;
            }
            printf("NULL\n");

            puts("ReveOrder:");
            p = n;
            while(p)
            {
                printf("%d ", p -> Item);
                p = p -> prev;
            }
            printf("NULL\n");
        }
        if(c == '2')
        {
            printf("\n删除:");
            scanf("%d", &X);
            p = head;
            deleteLL(p, X);
        }
        if(c == '3')
        {
            printf("\n插入(数据 位置):");
            scanf("%d %d", &X, &i);
            p = head;
            InsertLL(p, X, i);
        }
        if(c == '4')
            break;
    }
    return 0;
}