ReverseList.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24：反转链表
// 题目：定义一个函数，输入一个链表的头结点，反转该链表并输出反转后链表的
// 头结点。

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

ListNode* ReverseList(ListNode* pHead)
{
    ListNode* pReversedHead = nullptr;
    ListNode* pNode = pHead;
    ListNode* pPrev = nullptr;
    while(pNode != nullptr)
    {
        ListNode* pNext = pNode->m_pNext;

        if(pNext == nullptr)
            pReversedHead = pNode;

        pNode->m_pNext = pPrev;

        pPrev = pNode;
        pNode = pNext;
    }

    return pReversedHead;
}

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

    ListNode* pReversedHead = ReverseList(pHead);

    printf("The reversed list is: \n");
    PrintList(pReversedHead);

    return pReversedHead;
}

// 输入的链表有多个结点
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);

    ListNode* pReversedHead = Test(pNode1);

    DestroyList(pReversedHead);
}

// 输入的链表只有一个结点
void Test2()
{
    ListNode* pNode1 = CreateListNode(1);

    ListNode* pReversedHead = Test(pNode1);

    DestroyList(pReversedHead);
}

// 输入空链表
void Test3()
{
    Test(nullptr);
}

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

    return 0;
}