双向链表

#include<bits/stdc++.h>
using namespace std;
#define sc scanf
#define pr printf

typedef struct LNode
{
    int data;
    struct LNode *prior;
    struct LNode *next;
}LNode,*LinkList;

int tot = 0;
//创建双向链表 
void Create_LinkList(LinkList &L,int n)
{
    L = (LNode *)malloc(sizeof(LNode));
    L->data = n + 1; 
    LNode *q = L;
    
    for(int i = 1;i < n;i++)
    {
        LNode *p = (LNode *)malloc(sizeof(LNode));
        sc("%d",&p->data);
        q->next = p;
        p->prior = q;
        q = p;
    }

    if(n)
    {
        LNode *p = (LinkList)malloc(sizeof(LNode));
        sc("%d",&p->data);
        q->next = p;
        p->prior = q;
        p->next = L;
        L->prior = p;
    }
    else
    {
        L->next = L;
        L->prior = L;
    }

}

//获取双向链表第i个元素的指针位置
LinkList getelem_pos(LinkList &L,int i)
{
    int cnt = 0;
    LNode *p = L;
    while(p->next != L && cnt < i)
    {
        cnt++;
        p = p->next;
    }
    if(cnt == i)
    return p;
    else {
        puts("position is invalid! Please re-enter.");
        return NULL;
    }
} 

//双向链表插入元素
bool insert(LinkList &L,int i,int e)
{
    LNode *p,*q;
    if(!(p = getelem_pos(L,i)))//该位置不合法 
    return 0;
    //cout << "hello" << endl;
    
    LNode *s = (LNode *)malloc(sizeof(LNode));
    
//    if(s == NULL);//堆内存分配失败 
//    return 0;
    
    q = p->prior; //第i-1个结点
     
    s->data = e;
    
    q->next = s;
    s->prior = q;
    
    s->next = p;
    p->prior = s;
    
    return 1; 
} 

//删除第i个元素
bool delete_LinkList(LinkList &L,int i,int &e)
{
    LNode *p,*q;
    p = getelem_pos(L,i);
    
    if(p == NULL) return 0; //该位置不合法 
    //cout << p->data << endl;
    e = p->data;
    q = p->prior;
    q->next = p->next;
    (p->next)->prior = q;
    free(p);
    return 1;
} 

//遍历双向链表 
void deLinkList_Traver(LinkList &L)
{
   LNode *p = L;
   while(p->next != L)
   {
       p = p->next;
       tot++;
       cout << p->data << " " << (p->prior)->data << " " << (p->next)->data << endl;
   }
   //puts("");
}

//销毁链表 
void delete_Link(LinkList &L)
{
    int k;
     for(int i = 1;i <= tot;i++)
     delete_LinkList(L,1,k);
     
     free(L);//销毁头结点 
}
int main()
{
    int n;
    tot = 0;
    LinkList L;
    sc("%d",&n);
    Create_LinkList(L,n);
    deLinkList_Traver(L);
    bool ok = insert(L,2,7);
    //cout << ok << endl;
    cout << endl;
    if(ok)
    {
        deLinkList_Traver(L);
    }
    
    int e;
    ok = delete_LinkList(L,1,e);
    cout << endl;
    if(ok)
    {
        deLinkList_Traver(L);
    }
    
//    delete_Link(L);
//    deLinkList_Traver(L);
    return 0;
}