#include<iostream>
#include<stdio.h>
#include <string>
#include<conio.h>

typedef struct student
{
    int data;
    struct student *next;
    struct student *pre;
}dnode;

dnode *create() //尾插法建立带头结点的双链表
{
    dnode *head,*p,*s;
    int x=0;
    head=(dnode *)malloc(sizeof(dnode));
    head->data=0;
    head->pre=NULL;
    head->next=NULL;
    p=head;
    printf("please input data (end by 0):");
    scanf("%d",&x);
    while(x!=0)
    {
        s=(dnode *)malloc(sizeof(dnode));
        s->data=x;
        s->pre=p;
        s->next=p->next;
        p->next=s;
        p=s;
        printf("please input data (end by 0):");
        scanf("%d",&x);
    }
    return head;
};

void delnode(dnode *head,int num)
{
    dnode *p=head->next;
    while(p!=NULL)
    {
        if(num==p->data)
        {
            p->pre->next=p->next;
            if(p->next!=NULL)    //最后一个节点
                p->next->pre=p->pre;
            free(p);
            break;
        }
        p=p->next;
    }
    printf("could not find the node\n");
}


void display1(dnode *head)  //正向打印
{
    dnode *p=head->next;
    while(p!=NULL)
    {
        printf("%d  ",p->data);
        p=p->next;
    }
    printf("\n");
}
void display2(dnode *head)//反向打印
{
    dnode *p=head;
    while(p->next!=NULL)
    {
        p=p->next;
    }
    while(p->pre!=NULL)
    {
        printf("%d  ",p->data);
        p=p->pre;
    }
    printf("\n");
}



void main()
{
    dnode *head=create();
    delnode(head,4);
    display1(head);
    display2(head);
}