双向循环链表--增删查操作

双向循环链表与单链表区别其实不多，对比之后就是多了几个操作步骤

#include <stdio.h>#include <malloc.h>typedef int Elemtype;typedef struct LNode{    Elemtype data;    struct LNode *prior;    struct LNode *next;}LNode,*LinkList;LinkList MCreatlist_last(LinkList head,Elemtype n)//尾插法{    LinkList p;    LinkList q;//尾指针    int i;    head=(LinkList)malloc(sizeof(LNode));    head->next=head;    head->prior=head;    q=head;    for(i=0;i<n;i++)    {        p=(LinkList)malloc(sizeof(LNode));        scanf("%d",&p->data);        p->next=q->next;        p->prior=q;        q->next=p;        q=p;    }    head->prior=q;    return head;}void InsertList(LinkList head,int i,int e)//插入{    LinkList p,s;    int j=1;    p=head->next;    while(p!=head&&j<i)    {        p=p->next;        ++j;    }        s=(LinkList)malloc(sizeof(LNode));        s->data=e;        s->next=p->next;        p->next=s;        s->next->prior=s;        s->prior=p;       /* s->prior=p->prior;        p->prior->next=s;        s->next=p;        p->prior=s;*/      //  return head;}void deletelist(LinkList head,int i,int *e)//删除{    LinkList p,q;    int j=1;    p=head->next;    while(p->next&&j<i)    {        p=p->next;        j++;    }    //p=(LinkList)malloc(sizeof(LNode));   // *e=p->data;   q=p;    p->prior->next=p->next;    p->next->prior=p->prior;    *e=q->data;    free(p);}int Getelem(LinkList head,int i)//得到{    LinkList p;    int e;    int j=1;    p=head->next;    while(p&&j<i)    {        p=p->next;        ++j;    }    if(!p->next||j>i)        return 0;    else{        e=p->next->data;        return e;    }}int main(){    LinkList head,star;    int i=0;    int e;    int get;    head=MCreatlist_last(head,5);   /* star=head->next;    while(i<5)    {        printf("%d  ",star->data);        star=star->next;        ++i;    }*//*InsertList(head,3,2);     star=head->next;    while(i<6)    {        printf("%d  ",star->data);        star=star->next;        ++i;    }*/    deletelist(head,3,&e);    star=head->next;    while(i<4)    {        printf("%d  ",star->data);        star=star->next;        ++i;    }    printf("\n%d\n",e);    get=Getelem(head,3);    printf("%d",get);    return 0;}