018_01-在O(1)时间删除链表结点.cpp

/*******************************************************************
Copyright(c) 2016, Harry He
All rights reserved.
Distributed under the BSD license.
(See accompanying file LICENSE.txt at
https://github.com/zhedahht/CodingInterviewChinese2/blob/master/LICENSE.txt)
*******************************************************************/

//==================================================================
// 《剑指Offer——名企面试官精讲典型编程题》代码
// 作者：何海涛
//==================================================================

// 面试题18（一）：在O(1)时间删除链表结点
// 题目：给定单向链表的头指针和一个结点指针，定义一个函数在O(1)时间删除该
// 结点。

#include <cstdio>
#include "..\Utilities\List.h"

void DeleteNode(ListNode** pListHead, ListNode* pToBeDeleted)
{
    if(!pListHead || !pToBeDeleted)
        return;

    // 要删除的结点不是尾结点
    if(pToBeDeleted->m_pNext != nullptr)
    {
        ListNode* pNext = pToBeDeleted->m_pNext;
        pToBeDeleted->m_nValue = pNext->m_nValue;
        pToBeDeleted->m_pNext = pNext->m_pNext;
 
        delete pNext;
        pNext = nullptr;
    }
    // 链表只有一个结点，删除头结点（也是尾结点）
    else if(*pListHead == pToBeDeleted)
    {
        delete pToBeDeleted;
        pToBeDeleted = nullptr;
        *pListHead = nullptr;
    }
    // 链表中有多个结点，删除尾结点
    else
    {
        ListNode* pNode = *pListHead;
        while(pNode->m_pNext != pToBeDeleted)
        {
            pNode = pNode->m_pNext;            
        }
 
        pNode->m_pNext = nullptr;
        delete pToBeDeleted;
        pToBeDeleted = nullptr;
    }
}

// ====================测试代码====================
void Test(ListNode* pListHead, ListNode* pNode)
{
    printf("The original list is: \n");
    PrintList(pListHead);

    printf("The node to be deleted is: \n");
    PrintListNode(pNode);

    DeleteNode(&pListHead, pNode);
    
    printf("The result list is: \n");
    PrintList(pListHead);
}

// 链表中有多个结点，删除中间的结点
void Test1()
{
    ListNode* pNode1 = CreateListNode(1);
    ListNode* pNode2 = CreateListNode(2);
    ListNode* pNode3 = CreateListNode(3);
    ListNode* pNode4 = CreateListNode(4);
    ListNode* pNode5 = CreateListNode(5);

    ConnectListNodes(pNode1, pNode2);
    ConnectListNodes(pNode2, pNode3);
    ConnectListNodes(pNode3, pNode4);
    ConnectListNodes(pNode4, pNode5);

    Test(pNode1, pNode3);

    DestroyList(pNode1);
}

// 链表中有多个结点，删除尾结点
void Test2()
{
    ListNode* pNode1 = CreateListNode(1);
    ListNode* pNode2 = CreateListNode(2);
    ListNode* pNode3 = CreateListNode(3);
    ListNode* pNode4 = CreateListNode(4);
    ListNode* pNode5 = CreateListNode(5);

    ConnectListNodes(pNode1, pNode2);
    ConnectListNodes(pNode2, pNode3);
    ConnectListNodes(pNode3, pNode4);
    ConnectListNodes(pNode4, pNode5);

    Test(pNode1, pNode5);

    DestroyList(pNode1);
}

// 链表中有多个结点，删除头结点
void Test3()
{
    ListNode* pNode1 = CreateListNode(1);
    ListNode* pNode2 = CreateListNode(2);
    ListNode* pNode3 = CreateListNode(3);
    ListNode* pNode4 = CreateListNode(4);
    ListNode* pNode5 = CreateListNode(5);

    ConnectListNodes(pNode1, pNode2);
    ConnectListNodes(pNode2, pNode3);
    ConnectListNodes(pNode3, pNode4);
    ConnectListNodes(pNode4, pNode5);

    Test(pNode1, pNode1);

    DestroyList(pNode1);
}

// 链表中只有一个结点，删除头结点
void Test4()
{
    ListNode* pNode1 = CreateListNode(1);

    Test(pNode1, pNode1);
}

// 链表为空
void Test5()
{
    Test(nullptr, nullptr);
}

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

    return 0;
}