循環單鏈表（新版）

#include<iostream>
#include<stdlib.h>
using namespace std;
#define error -1

/*
create and operate a list with a head node.
*/

typedef struct Lnode
{
    int data;
    Lnode *next;
} Lnode;

void listInsertIntoTail(Lnode *&h,Lnode *&r,int data);

void listInit(Lnode *&h,Lnode *&r)
{
    h->next=h;
    r=h;
}

void listCreateByTail(Lnode *&h,Lnode *&r)//create a list by inserting into the tail always
{
    Lnode *newnode=(Lnode*)malloc(sizeof(Lnode));
    newnode->data=0;
    newnode->next=NULL;

    h->next=newnode;
    r=h->next;
    r->next=h;

    for(int i=1; i<6; i++)
    {
        listInsertIntoTail(h,r,i);
    }
}

void listInsertIntoTail(Lnode *&h,Lnode *&r,int x)//insert x into list
{
    Lnode *newnode=(Lnode*)malloc(sizeof(Lnode));
    newnode->data=x;
    newnode->next=NULL;

    r->next=newnode;
    r=r->next;
    r->next=h;
    newnode=NULL;
}

void deleteElem(Lnode *&h,int x)//delete the Element whose data equals x
{
    Lnode *temp1,*temp2;
    temp1=h;
    while(temp1->next->data!=x)//to find whose next node's data is x
    {
        temp1=temp1->next;
        if(temp1->next==h)//now, temp1 is the last node,it should break or it will leads to error.
        {
            break;
        }
    }
    if(temp1->next->data==x)
    {
        temp2=temp1->next;//to record the one needs to be deleted
        temp1->next=temp1->next->next;//adjust the list
        free(temp2);//delete node x
    }
    else
    {
        cout<<x<<" node dose not exist."<<endl;
    }
    temp1=NULL;
    temp2=NULL;
}

void listUpdate(Lnode *&h,int oldvlue,int newvalue)//replace old with new
{
    Lnode *temp=h;
    while(temp!=NULL)
    {
        if(temp->data==oldvlue)
        {
            temp->data=newvalue;
        }
        temp=temp->next;
        if(temp==h)
        {
            break;
        }
    }
    temp=NULL;
}

int findElem(Lnode *h,int x)//return x's position
{
    Lnode *temp=h;
    int position=0;
    while(temp->data!=x)
    {
        if(temp->next==h)
        {
            break;
        }
        temp=temp->next;
        position++;
    }
    if(temp->data==x)
    {
        return position;
    }
    else
    {
        return error;
    }
    temp=NULL;
}

void listDestroy(Lnode *&h,Lnode *&r)//release all space
{
    while(h->next!=h)
    {
        free(h);
        h=h->next;
        r->next=h;
    }
    free(r);
    cout<<"List is destroyed."<<endl;
}

void printstate(Lnode *&h)
{
    Lnode *temp=h->next;
    while(temp!=h)
    {
        cout<<temp->data<<" ";
        temp=temp->next;
    }
    cout<<endl;
    temp=NULL;
}

int main()
{
    Lnode *h=(Lnode*)malloc(sizeof(Lnode));
    Lnode *r=h;
    listInit(h,r);

    //listCreateByHead(h);
    cout<<"鏈表創建"<<endl;
    listCreateByTail(h,r);
    printstate(h);

    cout<<"刪除元素"<<endl;
    deleteElem(h,0);
    printstate(h);

    cout<<"更新元素"<<endl;
    listUpdate(h,2,-1);
    printstate(h);

    cout<<"查找元素"<<endl;
    cout<<findElem(h,-1)<<endl;

    cout<<"銷燬鏈表"<<endl;
    listDestroy(h,r);
    h=NULL;
    r=NULL;
    return 0;
}