4、循环链表

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　　1、知识点：

　　　　(1)、循环链表其实就是将单项链表的首尾连接起来。就是在链表的尾部添加一个指向头节点的指针(及在结束节点的next域中

的NULL值改成指向头节点的指针就行了)。

　　　　(2)、存在一个尾指针rear，在一些实际的例子中使用rear指针作为开始节点的情况是比较常见的。

　　　　(3)、图示（图片摘自百度）

                      

                        

                         

>>.分布代码

　　(1)、头插法创建循环链表(只带头指针的循环链表)

           

　　(2)、创建只带尾指针的循环链表(个人认为这个比较的好,当然在相应的情况下还是采取合适的解决方法)

         

　　(3)、循环链表是否为空

         

　　(4)、打印函数

         

　　(5)、链表的整合

         

　　(6)、销毁链表

         

(7)、说明

    在循环链表，一些关于增删改对链表的操作和前面的几节博客中的思路是一样一样的。

>>.全部代码

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

using namespace std;

#define OK                1
#define ERROR            0
#define OVERFLOW        -1

typedef int STATUS;
typedef int ElemType;

//创建循环链表的结构体
typedef struct CycleChain
{
    struct CycleChain* next;
    ElemType data;
}cycleChain;

//尾指针法创建循环链表，其实这是一个尾插法创建链表的方法
cycleChain* createCycleChain(cycleChain** headNode, cycleChain* rearNode, ElemType elem)
{
    //创建链表前判断headNode是否创建过。
    if((*headNode)==NULL && rearNode==NULL)
    {
        //没有创建headNode
        (*headNode) = (cycleChain*) malloc(sizeof(cycleChain));
        if(!(*headNode))
        {
            cout << "The head node is create faliure of cycle chain, Error!" << endl;
            exit(OVERFLOW);
        }
        (*headNode)->next = (*headNode);
        rearNode = (*headNode);
    }

    //创建新的节点，并插入链表
    cycleChain* newNode = NULL;
    newNode = (cycleChain*) malloc(sizeof(cycleChain));
    if(!newNode)
    {
        cout << "The new node is create failure of cycle chain, Error!" << endl;
        exit(OVERFLOW);
    }
    newNode->data = elem;

    newNode->next = rearNode->next;
    rearNode->next = newNode;
    rearNode = newNode;
    

    return rearNode;
}

//判断循环链表是否为空
bool emptyCycleChain(cycleChain* headNode)
{
    if(headNode->next == headNode)
        return true;
        //cout << "The cycle chain is empty!" << endl;
    else
        return false;
        //cout << "The cycke chain is not empty!" << endl;
}


//打印循环链表
STATUS printCycleChain(cycleChain* headNode)
{
    //首先判断此链表是否为空
    if(emptyCycleChain(headNode))
    {
        cout << "The cycle chain is empty, without data to printf!" ;
        return ERROR;
    }
    cycleChain* ptrNode;
    ptrNode = headNode->next;
    cout << "Cycle chain list:  ";
    while(ptrNode!=headNode)
    {
        cout << ptrNode->data << ", ";
        ptrNode = ptrNode->next;
    }
    return OK;
}

//两个循环链表的整合
STATUS connectionCycleChain(cycleChain* rearNode_A, cycleChain* rearNode_B)
{
    //将b表接到a表之后
    cycleChain* ptrNode = NULL;
    cycleChain* tmpNode = NULL;

    tmpNode = rearNode_B->next;
    ptrNode = rearNode_A->next;    //ptrNode指向头节点A

    //开始连接两表
    rearNode_A->next = tmpNode->next;
    rearNode_B->next = ptrNode;
    free(tmpNode);
    return OK;
}

//销毁循环链表
STATUS destroyCycleChain(cycleChain* headNode, cycleChain* rearNode)
{
    cycleChain* ptrNode = NULL;
    cycleChain* tmpNode = NULL;

    if(headNode->next==headNode)
    {
        //这里说明只有一个头节点的链表
        free(headNode);
        return OK;
    }
    
    tmpNode = headNode;
    while(tmpNode != rearNode)
    {
        ptrNode = tmpNode->next;
        free(tmpNode);
        tmpNode = ptrNode;
    }
    return OK;
}

int main(void)
{
    cout << "1:  创建循环链表" << endl;
    cout << "2:  打印循环链表" << endl;
    cout << "3:  判断链表为空" << endl;
    cout << "4:  链表的整合" << endl;
    cout << "5:  销毁循环链表" << endl;
    cout << "0:  退出程序" << endl << endl << endl;

    int choice = 0;
    int amount = 0;
    int i = 0;
    int elem = 0;
    cycleChain* headNode = NULL;
    cycleChain* rearNode = NULL;

    cycleChain* headNode_A = NULL;
    cycleChain* headNode_B = NULL;
    cycleChain* rearNode_A = NULL;
    cycleChain* rearNode_B = NULL;

    while(1)
    {
        cout << "Enter you choice: ";
        cin >> choice;

        switch(choice)
        {
        case 1:
            cout << "Enter amount of chain node: ";
            cin >> amount;
            cout << "Please enter the " << amount << " elem: ";
            for(i=0; i<amount; i++)
            {
                cin >> elem;
                rearNode = createCycleChain(&headNode, rearNode, elem);
            }
            cout << endl;
            break;
        case 2:
            cout << "Print List: " << endl;
            printCycleChain(headNode);
            cout << endl << endl;;
            break;
        case 3:
            cout << "The cycle chain if is empty:  ";
            if(emptyCycleChain(headNode))
                cout << "Yes !" << endl;
            else
                cout << "No !" << endl;
            cout << endl;
            break;
        case 4:
            cout << "Please enter first cycle chain of data:  " << endl;
            cout << "Enter amount of chain node: ";
            cin >> amount;
            cout << "Please enter the " << amount << " elem: ";
            for(i=0; i<amount; i++)
            {
                cin >> elem;
                rearNode_A = createCycleChain(&headNode_A, rearNode_A, elem);
            }

            cout << "Please enter second cycle chain of data:  " << endl;
            cout << "Enter amount of chain node: ";
            cin >> amount;
            cout << "Please enter the " << amount << " elem: ";
            for(i=0; i<amount; i++)
            {
                cin >> elem;
                rearNode_B = createCycleChain(&headNode_B, rearNode_B, elem);
            }
            connectionCycleChain(rearNode_A, rearNode_B);
            printCycleChain(headNode_A);
            cout << endl << endl;
            break;
        case 5:
            cout << "The cycle chain destory status:  ";
            if(destroyCycleChain(headNode, rearNode))
                cout << "successful!" << endl;
            else
                cout << "failure!" << endl;
            cout << endl;
            break;
        case 0:
            exit(0);
            break;
        }
    }

    return 0;
}

运行截图：