线性表实现——双向链表

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

#define OK 1
#define ERROR 0
typedef int Status;
typedef int ElemType;

typedef struct DNode
{
    ElemType data;
    struct DNode* next;
    struct DNode* front;
}DNode;

typedef struct DNode* DLinkList;

Status InitList(DLinkList* L)  //初始化操作，建立一个空的线性表.想把头指针里面的值改掉，所以传个头指针的地址
{
    *L = (DLinkList)malloc(sizeof(DNode));
    if (!(*L))
        return ERROR;
    (*L)->next = NULL;
    (*L)->front = NULL;
    return OK;
}
Status ListEmpty(DLinkList L)  //若线性表为空，返回true,否则返回false
{
    if (L->next == NULL)
        return OK;
    return ERROR;
}
Status ClearList(DLinkList* L) //清空线性表
{
    DLinkList p = (*L)->next;
    DLinkList q;
    while (p != NULL)
    {
        q = p;
        p = p->next;
        free(q);
    }
    (*L)->next = NULL;
    return OK;
}
Status GetElem(DLinkList L, int  i, ElemType *e)  //查找线性表中的第i个位置的元素值，并赋值给e
{
    int j = 0;
    while (L && j < i)
    {
        L = L->next;
        j++;
    }
    if (!L || j > i)
        return ERROR;
    *e = L->data;
    return OK;
}
Status LocateElem(DLinkList L, ElemType e) //查找线性表L中与给定值e相等的元素，如果查找成功，则返回第一个相同的元素在L中的下标；否则，返回0表示失败
{
    int i = 1;
    DLinkList p = L->next;
    while (p != NULL && p->data != e)
    {
        p = p->next;
        i++;
    }
    if (!p)
        return ERROR;
    return i;
}
Status ListInsert(DLinkList* L, int i, ElemType e)  //在线性表L的第i个位置插入元素e
{
    DLinkList p, q;
    p = *L;
    int j = 1;
    while (p && j<i)    //尾部插入时，p指向最后一个值，而j=i-1
    {
        p = p->next;
        j++;
    }
    if (!p || j > i)
        return ERROR;

    q = (DLinkList)malloc(sizeof(DNode));
    q->data = e;
    q->next = p->next;
    if(p->next)
        q->next->front = q;
    p->next = q;
    q->front = p;

    return ERROR;
}
Status ListDelete(DLinkList*L, int i, ElemType* e) //删除线性表L中第i个位置元素，并用e返回其值
{
    DLinkList p, q;
    p = *L;
    int j = 1;
    //while (p && j<i)
    while (p->next && j<i)
    {
        p = p->next;
        j++;
    }
    //if (!p || j > i)
    if (!(p->next) || j > i)
        return ERROR;
    q = p->next;
    *e = q->data;
    p->next = q->next;
    q->next->front = p;
    free(q);
    return OK;
}
Status CreateListHead(DLinkList *L, int n)
{
    DLinkList p;
    int i;
    (*L) = (DLinkList)malloc(sizeof(DNode));
    (*L)->next = NULL;
    for (i = 0; i < n; i++)
    {
        p = (DLinkList)malloc(sizeof(DNode));
        p->data = i;
        p->next = (*L)->next;
        if(p->next)
            p->next->front = p;
        p->front = *L;
        (*L)->next = p;
    }
    return OK;
}
Status CreateListTail(DLinkList *L, int n)
{
    DLinkList p;
    int i;
    (*L) = (DLinkList)malloc(sizeof(DNode));
    //(*L)->next = NULL;
    DLinkList q = (*L);
    for (i = 0; i < n; i++)
    {
        p = (DLinkList)malloc(sizeof(DNode));
        p->data = i + 10;
        q->next = p;
        p->front = q;
        q = p;
    }
    q->next = NULL;
    return OK;
}
Status visit(ElemType n)
{
    printf("-> %d  ", n);
    return OK;
}
Status ListTraverse(DLinkList L)
{
    DLinkList p = L->next;
    while (p != NULL)
    {
        visit(p->data);
        p = p->next;
    }
    return OK;
}

int ListLength(DLinkList L)  //返回线性表L的长度
{
    int i = 0;
    DLinkList p = L->next;
    while (p != NULL)
    {
        i++;
        p = p->next;
    }
    return i;
}

int main()
{
    DLinkList L;
    Status i, j;
    char opp = '-1';
    ElemType e;
    int pos = 1;
    int k = 0;

    i = InitList(&L);
    printf("链表L初始化完毕，ListLength(L)=%d\n\n", ListLength(L));

    printf("\n1.遍历操作 \n2.插入操作  \n3.删除操作 \n4.获取结点数据\n5.查找某个数是否在链表中 \n6.头插法创建链表 \n7.尾插法创建链表 \n8.置空链表 \n0.退出 \n请选择你的操作：\n");

    while (opp != '0') {
        scanf_s("%c", &opp);
        switch (opp) {
        case '1':
            ListTraverse(L);
            printf("\n");
            break;

        case '2':
            srand((unsigned)time(NULL));
            for (j = 1; j <= 10; j++)
            {
                i = ListInsert(&L, 1, rand() % 100);
            }
            printf("在L的表头依次插入10个随机数后：");
            ListTraverse(L);
            printf("\n");
            printf("链表L创建完毕，ListLength(L)=%d\n\n", ListLength(L));
            break;
        case '3':
            printf("要删除第几个元素？");
            scanf_s("%d", &pos);
            ListDelete(&L, pos, &e);
            printf("删除第%d个元素成功，现在链表为：\n", pos);
            ListTraverse(L);
            printf("\n");
            break;

        case '4':
            printf("你需要获取第几个元素？");
            scanf_s("%d", &pos);
            GetElem(L, pos, &e);
            printf("第%d个元素的值为：%d\n", pos, e);
            printf("\n");
            break;
        case '5':
            printf("输入你需要查找的数：");
            scanf_s("%d", &pos);
            k = LocateElem(L, pos);
            if (k)
                printf("第%d个元素的值为%d\n", k, pos);
            else
                printf("没有值为%d的元素\n", pos);
            printf("\n");
            break;
        case '6':
            CreateListHead(&L, 10);
            printf("整体创建L的元素(头插法)：\n");
            ListTraverse(L);
            printf("\n");
            break;

        case '7':
            CreateListTail(&L, 10);
            printf("整体创建L的元素(尾插法)：\n");
            ListTraverse(L);
            printf("\n");
            break;

        case '8':
            i = ClearList(&L);
            printf("\n清空L后：ListLength(L)=%d\n", ListLength(L));
            ListTraverse(L);
            printf("\n");
            break;

        case '0':
            exit(0);
        }
    }
}