用c语言编写程序数据结构

创建一个长度为6的双链表，要求在第三个结点之前任意插入一个新结点，并输出结果

代码如下，如有帮助，请帮忙采纳一下，谢谢。

代码：

#include <stdio.h>
#include <stdlib.h>
struct Node 
{
    int data;
    struct Node *pre,*next;
};


int main()
{
    struct Node* head = 0,*p,*t;
    int i,data;
    int pos;
    printf("请输入6个数字：");
    for (i=0;i<6;i++)
    {
        p = (struct Node*)malloc(sizeof(Node));
        scanf("%d",&data);
        p->data = data;
        p->next = NULL;
        if (head == 0)
        {
            head = p;
            head->pre = NULL;
            t = head;
            
        }else
        {
            t->next = p;
            p->pre = t;
            t = p;
        }
    }

    printf("请输入插入位置(1-3)和数据，以空格分隔：");
    scanf("%d %d",&pos,&data);
    p = (struct Node*)malloc(sizeof(Node));
    p->data = data;
    p->pre = NULL;
    p->next = NULL;
    if(pos == 1)
    {
        p->next = head;
        head->pre = p;
        head = p;
    }else
    {
        t = head;
        i = 1;
        while(i<pos-1)
        {
            t = t->next;
            i++;
        }
        p->next = t->next;
        p->pre = t;
        t->next = p;
        
    }
    //显示：
    t = head;
    while(t)
    {
        printf("%d ",t->data);
        t = t->next;
    }
    //释放空间
    while(head)
    {
        t = head->next;
        free(head); 
        head = t;
    }
    head =0;
    return 0;
}

参考：

假设第三个节点为q，第二个节点为p，新节点为r
r->next = q;
r->prev = p;
q->prev = r;
p->next = r;