数据结构——单链表及其操作

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

using namespace std;

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


//单链表的存储结构
typedef struct LNode
{
    ElemType data;            //结点的数据域
    struct LNode *next;        //结点的指针域
}LNode,*LinkList;            //LinkList为指向结构体LNode的指针类型


//初始化
Status InitList(LinkList &L)
{
    L = new LNode;    //生成新结点作为头结点，用头指针L指向头结点

    if (!L)            //分配失败
        return ERROR;

    L->next = NULL;    //头结点的指针域置空
    return OK;
}

//判断是否为空链表
bool ListEmpty(LinkList L)
{
    if(L->next == NULL)
        return true;
    else
        return false;
}

//返回单链表的长度
int ListLength(LinkList L)
{
    int length = 0;
    LinkList q = L;
    while(q->next != NULL)
    {
        q = q->next;
        length++;
    }
    return length;
}

//前插法创建单链表
//逆位序输入n个元素的值，建立带表头结点的单链表L
void CreateList_H(LinkList &L,int n)
{
    LinkList p;

    L = new LNode;
    L->next = NULL;        //先建立一个带头结点的空链表

    cout << "请依次输入" << n << "个元素：" << endl;

    for (int i = 0; i < n; i++)
    {
        p = new LNode;        //生成新结点*p
        cin >> p->data;        //输入元素值赋给新结点*p的数据域
        p->next = L->next;
        L->next = p;        //将新结点*p插入到头结点之后 (注意次序不能颠倒！！！
    }
}


//尾插法创建单链表
void CreateList_R(LinkList &L, int n)
{
    LinkList s, r;

    L = new LNode;
    L->next = NULL;        //先创建一个带头结点的空链表

    r = L;                //尾指针r指向头结点

    cout << "请依次输入" << n << "个元素：" << endl;

    for (int i = 0; i < n; i++)
    {
        s = new LNode;
        cin >> s->data;

        s->next = NULL;
        r->next = s;

        r = s;    //更新r的指向，r指向新的尾节点s
    }
}


//取值
//在带头结点的单链表L中根据序号i获取元素的值，用e返回L中第i个数据元素的值
Status GetElem(LinkList L, int i, ElemType &e)
{
    LinkList p;

    p = L->next;    //初始化，p指向首元结点
    int j = 1;        //计数器
    while (p && j < i)
    {
        p = p->next;    //p指向下一个结点
        j++;
    }
    if (!p || j > i)
        return ERROR;    //i值不合法，i>n 或 i<=0

    e = p->data;
    return OK;
}


//查找
//在带头结点的单链表L中查找值为e的元素
int LocateElem(LinkList L, ElemType e)
{
    LinkList p;

    p = L->next;    //初始化，p指向首元结点

    int n = 1;

    while (p && p->data != e)    //顺链域向后扫描，直到p为空或p所指向的结点数据域等于e
    {
        p = p->next;
        n++;
    }

    if (!p)
        return -1;

    return n;
}


//插入
//在带头结点的单链表L中第i个位置插入值为e的新结点
Status ListInsert(LinkList &L, int i, ElemType e)
{
    LinkList p;
    p = L;
    int j = 0;

    while (p && (j < i - 1))    //查找第i-1个结点，p指向该结点
    {
        p = p->next;
        j++;
    }
    if (!p || j > i - 1)
        return ERROR;

    LinkList s;
    s = new LNode;

    s->data = e;
    s->next = p->next;
    p->next = s;
    //注意这里的次序！！！

    return OK;
}


//删除
//在带头结点的单链表L中，删除第i个元素
Status ListDelete(LinkList &L, int i)
{
    LinkList p, q;
    p = L;
    int j = 0;
    while ((p->next) && (j < i - 1))    //查找第i-1个结点，p指向该结点
    {
        p = p->next;
        j++;
    }
    if (!(p->next) || (j > i - 1))
        return ERROR;

    q = p->next;
    p->next = q->next;

    delete q;

    return OK;
}

//单链表的销毁
void DestroyList(LinkList &L)
{
    LinkList q;
    while(L)
    {
        q = L;
        L = L->next;
        delete q;
    }
    L = NULL;
}

//清空单链表，仅保留头结点
void ClearList(LinkList &L)
{
    LinkList q;
    while(L->next)
    {
        q = L->next;
        L->next = q->next;
        delete q;
    }
}

//单链表的输出
void PrintList(LinkList L)
{
    LinkList p;

    p = L->next;

    while (p)
    {
        cout << p->data << " ";
        p = p->next;
    }
    cout << endl;
}

int main()
{
    int i, x, e, n, choose;
    LinkList L;
    L = NULL;    //这里不初始化为空，后面操作的时候vs上会报错，不太懂╮(╯▽╰)╭

    cout << "1. 初始化\n";

    cout << "2. 前插法创建单链表\n";

    cout << "3. 尾插法创建单链表\n";

    cout << "4. 取值\n";

    cout << "5. 查找\n";

    cout << "6. 插入\n";

    cout << "7. 删除\n";

    cout << "8. 销毁\n";

    cout << "9. 清空\n";

    cout << "10. 输出\n";

    cout << "0. 退出\n";

    choose = -1;

    while (choose != 0)
    {
        cout << "请选择操作：" << endl;
        cin >> choose;

        switch (choose)
        {
        case 1://初始化
            if (InitList(L))
                cout << "成功初始化一个空的单链表！\n";
            cout << endl;
            break;

        case 2://前插法创建单链表
            cout << "请输入所要创建的单链表的长度：";
            cin >> n;
            CreateList_H(L, n);
            cout << endl;
            break;

        case 3://尾插法创建单链表
            cout << "请输入所要创建的单链表的长度：";
            cin >> n;
            CreateList_R(L, n);
            cout << endl;
            break;

        case 4://单链表的取值
            cout << "请输入您要选取的元素的位置：";
            cin >> i;
            if (GetElem(L, i, e))
            {
                cout << "选取成功！" << endl;
                cout << "第" << i << "个元素是：" << e << endl;
            }
            else
                cout << "选取失败！" << endl;
            cout << endl;
            break;

        case 5://单链表的查找
            cout << "请输入您要查找的元素：";
            cin >> x;
            if (LocateElem(L, x) != -1)
            {
                cout << "查找成功！" << endl;
                cout << "该元素所在位置为：" << LocateElem(L,x) << endl;
            }
            else
                cout << "查找失败！" << endl;
            cout << endl;
            break;

        case 6://单链表的插入
            cout << "请输入选择插入的位置和元素：";
            cin >> i >> x;
            if (ListInsert(L, i, x))
                cout << "插入成功！" << endl;
            else
                cout << "插入失败！" << endl;
            cout << endl;
            break;

        case 7://单链表的删除
            cout << "请输入所要删除的元素位置：";
            cin >> i;
            if (ListDelete(L, i))
                cout << "删除成功！" << endl;
            else
                cout << "删除失败！" << endl;
            cout << endl;
            break;

        case 8://单链表销毁
            DestroyList(L);
            cout << "销毁成功！" << endl;
            break;

        case 9://单链表的清空
            ClearList(L);
            cout << "清空成功！" << endl;
            break;

        case 10://单链表的输出
            cout << "当前单链表中元素为：" << endl;
            PrintList(L);
            cout << endl;
            break;
        }
    }
    return 0;
}