双线链表基本操作不太懂

Question

双向链表的初始化、插入、删除等操作，最后得到的链表结果是与输入相反的 然后插入删除也实现不了 想问问哪里错了怎么改

//双向链表
#include<iostream>
#include<cstdlib>
#define ERROR 0
#define OK 0
typedef int Status;
typedef int Elemtype;
using namespace std;
typedef struct DuNode{
    Elemtype data;
    struct DuNode *next;
    struct DuNode *prior;
}DuNode,*DuLinkList;
DuLinkList p,q;
int j,i,e;
Status GetElem(DuLinkList La,int i,int &e){
    for(p=La->next,j=1;p&&j<i;j++){
        p=p->next;
    }
    if(!p||j>i) return ERROR;
    e=p->data;
    return OK;
}
Status DuListInsert(DuLinkList &La,int i,int e){//把e插到第i个位置 
    DuLinkList s=(DuLinkList)malloc(sizeof(DuNode));//新节点 
    for(j=1,p=La->next;j<i-1&&p;j++){
        p=p->next;
    }
    s->prior=p->prior;
    p->prior->next=s;
    return OK;
}
Status DuLinkDelete(DuLinkList &La,int i,Elemtype &e){
    for(j=1,p=La->next;j<i&&p;j++)//定位到位置i
    {
        p=p->next;
     } 
    if(!p||j>i) return ERROR;
    e=p->data;
    p->prior->next=p->next;
    p->next->prior=p->prior;
    free(p);
    return OK; 
}
Status DuCreatList(DuLinkList &L,int n){
    L=(DuLinkList)malloc(sizeof(DuNode));
    L->next=NULL;
    for(int i=n;i>0;i--){
        DuLinkList s=(DuLinkList)malloc(sizeof(DuNode));
        cin>>s->data;
        s->next=L->next;
        s->prior=L;
        L->next=s;
    }
    return OK;
}
int main(){
    DuLinkList p=(DuLinkList)malloc(sizeof(DuNode));
    DuLinkList L;
    cout<<"原链表中数的个数"<<endl;
    int n;
    cin>>n;
    cout<<"原链表中的数"<<endl;
    DuCreatList(L,n);
    cout<<"现在的链表为："<<endl;
    for(p=L->next;p;p=p->next){
        cout<<p->data<<" ";
    } 
    cout<<endl;
    cout<<"想得到数的位置：";
    cin>>i;
    if(GetElem(L,i,e)){
        cout<<"第"<<i<<"个数是"<<e<<endl; 
    } 
    else cout<<"获取失败"<<endl;
    //添加元素
    cout<<"添加位置"<<endl;
    cin>>i;
    cout<<"添加元素的值"<<endl;
    cin>>e;
    if(DuListInsert(L,i,e)){
        cout<<"插入成功 此时的链表为： ";
        for(p=L->next;p;p=p->next){
            cout<<p->data<<" ";
        } 
        cout<<endl;
    } 
    else cout<<"插入失败"<<endl;
    //删除元素
    cout<<"删除位置";
    cin>>i;
    if(DuLinkDelete(L,i,e)){
        cout<<"删除成功"<<"删除的值为"<<e<<endl;
        cout<<"此时链表为：" <<endl;
        for(p=L->next;p;p=p->next){
            cout<<p->data<<" ";
        } 
    } 
    else cout<<"删除失败"<<endl; 
    }

Answer 1

main开头的p申请空间不是白忙乎了么
#define ERROR 0
#define OK 0
你把ERROR和OK都定义成0了，这还能对啊
insert函数你没有考虑p为空的情况
如下是改好的：

//双向链表
#include<iostream>
#include<cstdlib>
#define ERROR 0
#define OK 1
typedef int Status;
typedef int Elemtype;
using namespace std;
typedef struct DuNode{
    Elemtype data;
    struct DuNode *next;
    struct DuNode *prior;
}DuNode,*DuLinkList;
DuLinkList p,q;
int j,i,e;
Status GetElem(DuLinkList La,int i,int &e){
    for(p=La->next,j=1;p&&j<i;j++){
        p=p->next;
    }
    if(!p||j>i) return ERROR;
    e=p->data;
    return OK;
}
Status DuListInsert(DuLinkList &La,int i,int e){//把e插到第i个位置 
    DuLinkList s=(DuLinkList)malloc(sizeof(DuNode));//新节点 
    s->data = e;
    DuLinkList q = La;
    for(j=1,p=La->next;j<i-1&&p;j++){
        p=p->next;
        q=q->next;
    }
    if(!p||j>i) return ERROR;
    s->next = q->next;
    s->prior= q;
    q->next->prior = s;
    q->next=  s;
    return OK;
}
Status DuLinkDelete(DuLinkList &La,int i,Elemtype &e){
    for(j=1,p=La->next;j<i&&p;j++)//定位到位置i
    {
        p=p->next;
     } 
    if(!p||j>i) return ERROR;
    e=p->data;
    p->prior->next=p->next;
    p->next->prior=p->prior;
    free(p);
    return OK; 
}
Status DuCreatList(DuLinkList &L,int n){
    L=(DuLinkList)malloc(sizeof(DuNode));
    L->next=NULL;
    for(int i=n;i>0;i--){
        DuLinkList s=(DuLinkList)malloc(sizeof(DuNode));
        cin>>s->data;
        s->next=L->next;
        if(L->next != NULL)
            L->next->prior = s;
        s->prior=L;
        L->next=s;
    }
    return OK;
}
int main(){
    DuLinkList p;
    DuLinkList L;
    cout<<"原链表中数的个数"<<endl;
    int n;
    cin>>n;
    cout<<"原链表中的数"<<endl;
    DuCreatList(L,n);
    cout<<"现在的链表为："<<endl;
    for(p=L->next;p;p=p->next){
        cout<<p->data<<" ";
    } 
    cout<<endl;
    cout<<"想得到数的位置：";
    cin>>i;
    if(GetElem(L,i,e)){
        cout<<"第"<<i<<"个数是"<<e<<endl; 
    } 
    else cout<<"获取失败"<<endl;
    //添加元素
    cout<<"添加位置"<<endl;
    cin>>i;
    cout<<"添加元素的值"<<endl;
    cin>>e;
    if(DuListInsert(L,i,e)){
        cout<<"插入成功 此时的链表为： ";
        for(p=L->next;p;p=p->next){
            cout<<p->data<<" ";
        } 
        cout<<endl;
    } 
    else cout<<"插入失败"<<endl;
    //删除元素
    cout<<"删除位置";
    cin>>i;
    if(DuLinkDelete(L,i,e)){
        cout<<"删除成功"<<"删除的值为"<<e<<endl;
        cout<<"此时链表为：" <<endl;
        for(p=L->next;p;p=p->next){
            cout<<p->data<<" ";
        } 
    } 
    else cout<<"删除失败"<<endl; 
    }