JZ-C-27

剑指offer第二十七题：二叉搜索树和双向链表

//============================================================================
// Name        : JZ-C-27.cpp
// Author      : Laughing_Lz
// Version     :
// Copyright   : All Right Reserved
// Description : 二叉搜索树和双向链表
//============================================================================

#include <iostream>
#include <stdio.h>
#include "BinaryTree.h"
using namespace std;
void ConvertNode(BinaryTreeNode* pNode, BinaryTreeNode** pLastNodeInList);

BinaryTreeNode* Convert(BinaryTreeNode* pRootOfTree) {
    BinaryTreeNode* pLastNodeInList = NULL;
    ConvertNode(pRootOfTree, &pLastNodeInList); //遍历二叉搜索树，并转换为双向链表
    // pLastNodeInList指向双向链表的尾结点，
    // 我们需要返回头结点
    BinaryTreeNode *pHeadOfList = pLastNodeInList;
    while (pHeadOfList != NULL && pHeadOfList->m_pLeft != NULL) {
        pHeadOfList = pHeadOfList->m_pLeft;
    }
    return pHeadOfList;
}
/**
 * 遍历二叉搜索树，并转换为双向链表
 */
void ConvertNode(BinaryTreeNode* pNode, BinaryTreeNode** pLastNodeInList) {
    if (pNode == NULL) {
        return;
    }
    BinaryTreeNode *pCurrent = pNode;    //★
    if (pCurrent->m_pLeft != NULL) {
        ConvertNode(pCurrent->m_pLeft, pLastNodeInList);
    }
    /*****★★★★★重点看这里★★★★★******/
    pCurrent->m_pLeft = *pLastNodeInList;//前一个结点
    if(*pLastNodeInList != NULL){
        (*pLastNodeInList)->m_pRight = pCurrent;//后一个结点
    }
    *pLastNodeInList = pCurrent;//双向链表的最后一个结点，位置向后移动一位

    if (pCurrent->m_pRight != NULL) {
        ConvertNode(pCurrent->m_pRight, pLastNodeInList);
    }
}
// ====================测试代码====================
void PrintDoubleLinkedList(BinaryTreeNode* pHeadOfList)
{
    BinaryTreeNode* pNode = pHeadOfList;

    printf("The nodes from left to right are:
");
    while(pNode != NULL)
    {
        printf("%d	", pNode->m_nValue);

        if(pNode->m_pRight == NULL)
            break;
        pNode = pNode->m_pRight;
    }

    printf("
The nodes from right to left are:
");
    while(pNode != NULL)
    {
        printf("%d	", pNode->m_nValue);

        if(pNode->m_pLeft == NULL)
            break;
        pNode = pNode->m_pLeft;
    }

    printf("
");
}

void DestroyList(BinaryTreeNode* pHeadOfList)
{
    BinaryTreeNode* pNode = pHeadOfList;
    while(pNode != NULL)
    {
        BinaryTreeNode* pNext = pNode->m_pRight;

        delete pNode;
        pNode = pNext;
    }
}

void Test(char* testName, BinaryTreeNode* pRootOfTree)
{
    if(testName != NULL)
        printf("%s begins:
", testName);

    PrintTree(pRootOfTree);

    BinaryTreeNode* pHeadOfList = Convert(pRootOfTree);

    PrintDoubleLinkedList(pHeadOfList);
}

//            10
//         /      
//        6        14
//       /        /
//      4  8     12  16
void Test1()
{
    BinaryTreeNode* pNode10 = CreateBinaryTreeNode(10);
    BinaryTreeNode* pNode6 = CreateBinaryTreeNode(6);
    BinaryTreeNode* pNode14 = CreateBinaryTreeNode(14);
    BinaryTreeNode* pNode4 = CreateBinaryTreeNode(4);
    BinaryTreeNode* pNode8 = CreateBinaryTreeNode(8);
    BinaryTreeNode* pNode12 = CreateBinaryTreeNode(12);
    BinaryTreeNode* pNode16 = CreateBinaryTreeNode(16);

    ConnectTreeNodes(pNode10, pNode6, pNode14);
    ConnectTreeNodes(pNode6, pNode4, pNode8);
    ConnectTreeNodes(pNode14, pNode12, pNode16);

    Test("Test1", pNode10);

    DestroyList(pNode4);
}

//               5
//              /
//             4
//            /
//           3
//          /
//         2
//        /
//       1
void Test2()
{
    BinaryTreeNode* pNode5 = CreateBinaryTreeNode(5);
    BinaryTreeNode* pNode4 = CreateBinaryTreeNode(4);
    BinaryTreeNode* pNode3 = CreateBinaryTreeNode(3);
    BinaryTreeNode* pNode2 = CreateBinaryTreeNode(2);
    BinaryTreeNode* pNode1 = CreateBinaryTreeNode(1);

    ConnectTreeNodes(pNode5, pNode4, NULL);
    ConnectTreeNodes(pNode4, pNode3, NULL);
    ConnectTreeNodes(pNode3, pNode2, NULL);
    ConnectTreeNodes(pNode2, pNode1, NULL);

    Test("Test2", pNode5);

    DestroyList(pNode1);
}

// 1
//  
//   2
//    
//     3
//      
//       4
//        
//         5
void Test3()
{
    BinaryTreeNode* pNode1 = CreateBinaryTreeNode(1);
    BinaryTreeNode* pNode2 = CreateBinaryTreeNode(2);
    BinaryTreeNode* pNode3 = CreateBinaryTreeNode(3);
    BinaryTreeNode* pNode4 = CreateBinaryTreeNode(4);
    BinaryTreeNode* pNode5 = CreateBinaryTreeNode(5);

    ConnectTreeNodes(pNode1, NULL, pNode2);
    ConnectTreeNodes(pNode2, NULL, pNode3);
    ConnectTreeNodes(pNode3, NULL, pNode4);
    ConnectTreeNodes(pNode4, NULL, pNode5);

    Test("Test3", pNode1);

    DestroyList(pNode1);
}

// 树中只有1个结点
void Test4()
{
    BinaryTreeNode* pNode1 = CreateBinaryTreeNode(1);
    Test("Test4", pNode1);

    DestroyList(pNode1);
}

// 树中没有结点
void Test5()
{
    Test("Test5", NULL);
}

int main(int argc, char** argv)
{
    Test1();
    Test2();
    Test3();
    Test4();
    Test5();

    return 0;
}