1.2单链表的基本操作

#include <iostream>
using namespace std;
#define OK 1
#define ERROR 0
typedef int ElemType;
typedef int Status;

//单链表的存储结构
typedef struct LNode
{
    ElemType data;
    struct LNode *next;
} LNode,*LinkList;

//初始化
Status InitList(LinkList &L)
{
    L=new LNode;
    L->next=NULL;
    return OK;
}
//销毁
Status DestroyList(LinkList &L)
{
       LinkList p;
       while(L)
        {
            p=L;
            L=L->next;
            delete p;
        }
       return OK;
 }
//清空
Status ClearList(LinkList L)
{// 将L重置为空表
   LinkList p,q;
   p=L->next;   //p指向第一个结点
   while(p)       //没到表尾
       {q=p->next; delete p; p=q;}
   L->next=NULL;   //头结点指针域为空
   return OK;
 }
//求长度
int  ListLength(LinkList L)
{  //返回L中数据元素个数
    LinkList p=L->next; //p指向第一个结点
    int count=0;
    while(p){//遍历单链表,统计结点数
        ++count;
        p=p->next;
    }
    return count;
 }
//判断是否为空
bool ListEmpty(LinkList L)
{//若L为空表，则返回true，否则返回false
   if(L->next==NULL)
       return true;
   else
       return false;
 }
//取值
Status GetElem(LinkList L,int i,ElemType &e)
{
    LinkList p=L->next;
    int j=1;
    while(p&&j<i)
    {
        p=p->next;
        ++j;
    }
    if(!p||j>i) return ERROR;
    e=p->data;
    return OK;
}
//按值查找
LNode *LocateElem(LinkList L,ElemType e)
{
    LinkList p=L->next;
    while(p &&p->data!=e)
        p->next;
    return p;
}
//插入
Status ListInsert(LinkList &L,int i,ElemType e)
{
    LinkList p=L;
    int j=0;
    while(p && (j<i-1))
    {
        p=p->next;
        ++j;
    }
    if(!p||j>i-1) return ERROR;
    LinkList s=new LNode;
    s->data=e;
    s->next=p->next;
    p->next=s;
    return OK;
}
//删除
Status ListDelete(LinkList &L,int i)
{
    LinkList p=L;
    int j=0;
    while((p->next)&&(j<i-1))
    {
        p=p->next;
        ++j;
    }
    if(!(p->next)||(j>i-1)) return ERROR;
    LinkList q=p->next;
    p->next=q->next;
    delete q;
    return OK;
}
//前插法创建单链表
void CreateList_H(LinkList &L,int n)
{
    L=new LNode;
    L->next=NULL;
    for(int i=0; i<n; ++i)
    {
        LinkList p=new LNode;
        cin>>p->data;
        p->next=L->next;
        L->next=p;
    }
}
//后插法创建单链表
void CreateList_R(LinkList &L,int n)
{
    L=new LNode;
    L->next=NULL;
    LinkList r=L;
    for(int i=0; i<n; ++i)
    {
        LinkList p=new LNode;
        cin>>p->data;
        p->next=NULL;
        r->next=p;
        r=p;
    }
}
//查找哪个元素的前驱
Status ListPrior(LinkList L,ElemType cur_e,ElemType *pre_e)
{
	LinkList q=L->next;//第一个结点
	if(!q)//若链表为空
	    return ERROR;
	LinkList p=q->next;//第二个结点
	while(p)
	{
		if(p->data==cur_e)
		{
			*pre_e=q->data;
			return OK;
		}
		else
		{
			q=p;
			p=p->next;
		}
	}
    return ERROR;
}
//查找哪个元素的后继
Status ListNext(LinkList L,ElemType cur_e,ElemType *next_e)
{
	LinkList p=L->next;
	while(p)
	{
		if(p->data==cur_e&&p->next)
		{
			*next_e=p->next->data;
			return OK;
		}
		else
		    p=p->next;
	}
	return ERROR;
}
//显示线性表
void DisplayList(LinkList L)
{
    LinkList p=L->next;
    while(p)
    {
        cout<<p->data<<"  ";
        p=p->next;
    }
    cout<<endl;
    return;
}
void show_help()
{
    cout<<"******* Data Structure ******"<<endl;
    cout<<"1----清空线性表"<<endl;
    cout<<"2----判断线性表是否为空"<<endl;
    cout<<"3----求线性表长度"<<endl;
    cout<<"4----获取线性表指定位置元素"<<endl;
    cout<<"5----求前驱"<<endl;
    cout<<"6----求后继"<<endl;
    cout<<"7----在线性表指定位置插入元素"<<endl;
    cout<<"8----删除线性表指定位置元素"<<endl;
    cout<<"9----显示线性表"<<endl;
    cout<<"     退出，输入0"<<endl;

}
int main()
{
    char operate_code;
    show_help();
    LinkList L;
    InitList(L);
    ElemType e;
    int i,n;
    printf("请输入链表的个数\n");
    scanf("%d",&n);
    CreateList_H(L,n); 
    while(1)
    {
        cout<<"请输入操作代码:";
        cin>>operate_code;
        if(operate_code=='1')
        {
            cout<<"The list has been cleared."<<endl;
            ClearList(L);//调用操作函数

        }
        else if (operate_code=='2')
        {
            if(ListEmpty(L))
                cout<<"The list is empty."<<endl;
            else
                cout<<"The list is not empty."<<endl;

        }
        else if (operate_code=='3')
        {
            cout<<"The length of list is:"<<ListLength(L)<<endl;

        }
        else if (operate_code=='4')
        {
            cout<<"请输入指定的位置："<<endl;
            cin>>i;
            if(GetElem(L,i,e) == 1) cout<<"这个位置的数据是："<<e<<endl;
            else cout <<"error"<<endl;
        }
        else if (operate_code=='5')
        {
            int n;
            cout<<"请输入你想查找哪个元素的前驱："<<endl;
            cin>>n;
            if(ListPrior(L,n,&e) == 1) cout<<n<<"的前驱为："<<e<<endl;
                else cout<<"error"<<endl;
        }
        else if (operate_code=='6')
        {
            int n;
            cout<<"请输入你想查找哪个元素的后继："<<endl;
            cin>>n;
            if(ListNext(L,n,&e)==1) cout<<n<<"的后继为："<<e<<endl;
                else cout<<"error"<<endl;
        }
        else if (operate_code=='7')
        {
            cout<<"请输入插入元素及其位置："<<endl;
            cin>>e>>i;
            if(ListInsert(L,i,e)==ERROR) cout<<"您的输入不合法"<<endl;

        }
        else if (operate_code=='8')
        {
            cout<<"请输入你想要删除哪个位置的元素："<<endl;
            cin>>i;
            if(ListDelete(L,i)==ERROR)  cout<<"error"<<endl;

        }
        else if (operate_code=='9')
        {
            cout<<"The contents of the list are:"<<endl;
            DisplayList(L);

        }
        else if (operate_code=='0')
        {
            break;
        }
        else
        {
            cout<<"\n操作码错误！！！"<<endl;
            show_help();
        }
    }
    //调用销毁线性表函数，如Destroy_List(L);
    DestroyList(L);
    return 0;
}