double

#include<stdio.h>
#include<stdlib.h>


typedef struct DOUBLE_LIST
{
    int data;
    struct DOUBLE_LIST *prev;
    struct DOUBLE_LIST *next;
}double_list;

double_list *createlist()       //创建有n个元素的双向链表 并输入元素
{
    double_list *head, *p, *q;
    int n,x;
	int i;
    head = (double_list *)malloc(sizeof(double_list));
    head->prev = head;
    head->next = head;
    p = head;
    printf("Enter the number of elements to create a double linked list:\n");
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
        scanf("%d", &x);
        q = (double_list *)malloc(sizeof(double_list));
        q->data = x;
        p->next = q;
        head->prev = q;
        q->prev = p;
        q->next = head;
        p = q;
    }
    return head;
}
//遍历并且输出这些元素
void printlist(double_list *head)
{
    double_list *p;
    p = head;
    p = p->next;
    while(p!=head)
    {
        printf("%d  ", p->data);
        p = p->next;
    }
    printf("\n");
}
//得到现在双向链表中的元素的个数
int lengthlist(double_list *head)
{
    double_list *p;
    p = head;
    p = p->next;
    int coun = 0;
    while(p!=head)
    {
        coun++;
        p = p->next;
    }
    return coun;
}
//在第i个元素之前插入数据data
void insertlist_f(double_list *head, int i, int data)
{
    double_list *p = head, *q;
    p = p->next;
    i--;
    while(i--)
        p = p->next;
    q = (double_list *)malloc(sizeof(double_list));
    q->data = data;
    (p->prev)->next = q;
    q->prev = p->prev;
    q->next = p;
    p->prev = q;
}
//删除第i个位置的元素
void deletelist_i(double_list *head, int i)
{
    double_list *p = head;
    p = p->next;
    i--;
    while(i--)
        p = p->next;
    (p->prev)->next = p->next;
    (p->next)->prev = p->prev;
    free(p);
}
//删除值为x的元素
void deletelist_x(double_list *head, int x)
{
    double_list *p = head, *q;
    p = p->next;
    while(p!=head)
        if(p->data == x)
        {
            q = p->next;
            (p->prev)->next = p->next;
            (p->next)->prev = p->prev;
            free(p);
            p = q;
        }
        else
            p = p->next;
}
//对双向链表进行排序
void sortlist(double_list *head)  //升序
{
    double_list *p = head, *q, *t;
    p = p->next;
    for(;p!=head;p=p->next)
        for(t = p->next;t!=head;t=t->next)
        {
            if(p->data > t->data)
            {
                int a = p->data;
                p->data = t->data;
                t->data = a;
            }
        }
}
int main()
{
    double_list *head;
    head = createlist();
	printf("printlist=============\n");
    printlist(head);

	printf("deletelist_x===2==========\n");

	deletelist_x(head, 2);
    //sortlist(head);
	printf("printlist=============\n");
    printlist(head);
	printf("insertlist_f===2===2=======\n");
    insertlist_f(head, 2, 2);
	printf("printlist=============\n");
    printlist(head);
 
    return 0;
}


/*
[email protected]:~/lin/ms$ ./a.out                
Enter the number of elements to create a double linked list:
6
1
2
3
4
5
6
printlist=============
1  2  3  4  5  6  
deletelist_x===2==========
printlist=============
1  3  4  5  6  
insertlist_f===2===2=======
printlist=============
1  2  3  4  5  6  
[email protected]:~/lin/ms$ 

*/