这是一个双向循环链表，要实现插入和删除的功能？能够插入节点但是不能插入尾节点？不知道该怎么改代码？
#include "stdafx.h"
#include "stdio.h"
#include "stdlib.h"
#define     OK      1
#define        ERROR    -1
#define     NULL   0
typedef        int ElemType;  
typedef     int Status;
typedef struct node   
{
    int data;
    struct node *prior;
    struct node *next;
}Lnode,*DuLinklist;

void creat(DuLinklist &L)
{
    DuLinklist p,q;
    int i;
    L=(DuLinklist)malloc(sizeof(Lnode));
    L->next=L;
    L->prior=L;
    q=L;
    for(i=1;i<=5;i++)
    {
        p=(DuLinklist)malloc(sizeof(Lnode));
        printf("input number:\n");
        scanf("%d",&p->data);
        p->next=L->prior;
        p->prior=q;
        q->next=p;
        q=p;
    }
}

void print(DuLinklist L)
{
    DuLinklist p;
    p=L->next;
    while(p!=L)
    {
        printf("%5d",p->data);
        p=p->next;
    }
    printf("\n");
}

Status insert(DuLinklist &L,int i,ElemType e)//不能够插入一个元素到尾节点？代码改如何修改？
{
    DuLinklist p;
    DuLinklist s;
    p=L->next;
    int j=0;
    int m=5;
        
    if(i<1)
    {
        return ERROR;
    }
    if(i<=m&&i>=1)
    {
        while(p&&j<i-1)
        {
            p=p->next;
            ++j;
        }
        s=(DuLinklist)malloc(sizeof(Lnode));
        s->data=e;
        s->prior=p->prior;
        p->prior->next=s;
        s->next=p;
        p->prior=s;
    }
    if(i>m)
    {
        s=(DuLinklist)malloc(sizeof(Lnode));
        s->data=e;
        s->prior=L->prior;
        L->prior->next=s;
        s->next=L;
        L->prior=s;
    }   
    return OK;
}

Status Delete(DuLinklist &L,int i,ElemType e)
{
    DuLinklist p;
    int m=5;
    int j=0;
    p=L->next;
    while(p&&j<i-1)
    {
        p=p->next;
        ++j;
    }
    if(i<1)
    {
        return ERROR;
    }
    if(i<=m&&i>=1)
    {
        e=p->data;
        p->prior->next=p->next;
        p->next->prior=p->prior;
        free(p);
    }
    if(i>m)
    {
        e=p->data;
        p->prior->next=p->next;
        p->next->prior=p->prior;
        free(p);
    }
        return OK;
}

int main(int argc, char* argv[])
{
    DuLinklist L;
    int i=0;
    int e=0;
    creat(L);
    print(L);
    printf("\n");
    printf("input weizhi:\n");
    scanf("%d",&i);
    printf("input insert_number:\n");
    scanf("%d",&e);
    insert(L,i,e);
    print(L);
    printf("\n");
    printf("input delete_address:\n");
    scanf("%d",&i);
    Delete(L,i,e);
    print(L);
    return 0;
}

个人觉得creat函数应该这么定义：
void creat(DuLinklist L){
    DuLinklist q,p;
    int i;
    L=(DuLinklist)malloc(sizeof(Lnode));
    L->next=NULL;
    L->prior=NULL;
    q=L;
    for(i=1;i<=5;i++){
        p=(DuLinklist)malloc(sizeof(Lnode));
        printf("input number:\n");
        scanf("%d",&p->data);
        p->next=q->next; //新节点的后继为头结点的原后继
        q->next->prior=p;//头结点的原后继节点的前继为新节点，昨晚疏忽忘记了！~
        p->prior=q;     //新节点的前继为头结点
        q->next=p;     //头节点的后继改为新节点
        q=L;         //头结点不动
    }
}
 
然后在插入的时候代码改成这样：
if(i<=m&&i>=1)
    {
        while(p&&j<i-1)
        {
            p=p->next;
            ++j;
        }
        s=(DuLinklist)malloc(sizeof(Lnode));
        s->data=e;
        s->prior=p;  //s的前继就是原尾节点
        p->next=s;   //原尾节点的后继为s
        s->next=p->next; //s的后继为原尾节点的后继
    }
 


[ 本帖最后由 plumblossom 于 2009-10-20 21:02 编辑 ]