20、双向链表

#define _CRT_SECURE_NO_WARNINGS

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#define OK 1
#define ERROR 0
#define TRUE 1
#define FALSE 0

typedef int ElemType;
typedef int Status;
typedef struct DuLNode {
    ElemType data;
    struct DuLNode *prior;
    struct DuLNode *next;
}DuLNode,*DuLinkList;
//初始化链表
void Init_DuL(DuLinkList &L) {
    L = (DuLinkList)malloc(sizeof(DuLNode));
    L->data = NULL;
    L->next = L;
    L->prior = L;
}
//链表长度
Status Length_DuL(DuLinkList &L) {
    DuLinkList p;
    p = L->next;
    int i=0;
    while (p->data != NULL) {
        p = p->next;
        i++;
    }
    return i;
}

DuLinkList GetElemP_DuL(DuLinkList &L, int i) {
    DuLinkList p = L->next;
    int j = 1;
    while (p&&j < i) {//p不为空或者计数器j还没有等于i时，循环继续
        p = p->next; ++j;
    }
    if (!p || j>i || i>(Length_DuL(L) + 1)) {//第i个元素不存在或i大于表长加1时，p指向空
        p=NULL;
    }
    if (i == Length_DuL(L) + 1) {//i等于表长加1时，p指向头结点
        p = L;
    }
    return p;
}

Status ListInsert_DuL(DuLinkList &L, int i, ElemType e) {
    //在带条结点的双链循环线性表L中第i个位置之前插入元素e
    //i的合法值为1<=i<=表长+1
    DuLinkList p,s;
    if (!(p = GetElemP_DuL(L, i)))//在L中确定插入位置指针p
        return ERROR;
    if (!(s = (DuLinkList)malloc(sizeof(DuLNode)))) {
        return ERROR;
    }
    s->data = e;
    s->prior = p->prior;
    p->prior->next = s;
    s->next = p;
    p->prior = s;
    return OK;
}
//删除带头结点的双链循环线性表L的第i个元素
Status ListDelete_DuL(DuLinkList &L, int i, ElemType &e) {
    DuLinkList p;
    if (!(p = GetElemP_DuL(L, i))) {//在L中确定第i个元素的位置指针
        return ERROR;                //p=NULL，即第i个元素不存在
    }
    e = p->data;
    p->prior->next = p->next;
    p->next->prior = p->prior;
    free(p);
    return OK;
}
//释放销毁
void Destory_DuL(DuLinkList &L) {
    DuLinkList p,q;
    p = L->next;
    while (p->data != NULL) {
        q = p->next;
        p->prior->next = p->next;
        p->next->prior = p->prior;
        free(p);
        p = q;
    }
    free(L);
}

//输出打印
void printf_DuL(DuLinkList &L) {
    DuLinkList p;
    p = L->next;
    for (int i = 0; i < Length_DuL(L); i++) {
        printf("%d ", p->data);
        p = p->next;
    }
    printf("
");
}

int main()
{
    DuLinkList list;
    ElemType a[] = { 11,22,33,44,55,66 };
    ElemType e;
    //初始化
    Init_DuL(list);
    //插入数据
    for (int i = 0; i < 6; i++) {
        ListInsert_DuL(list, i+1, a[i]);
    }
    //输出
    printf_DuL(list);
    printf("删除前长度：%d
", Length_DuL(list));
    //删除
    ListDelete_DuL(list, 1, e);
    //输出
    printf_DuL(list);
    printf("删除后长度：%d
", Length_DuL(list));
    printf("删除的元素：%d
", e);

    //销毁
    Destory_DuL(list);

    printf("
");
    system("pause");
    return 0;
}

VS2015运行结果：