《剑指offer》第十八题（删除链表中重复的结点）

// 面试题18（二）：删除链表中重复的结点
// 题目：在一个排序的链表中，如何删除重复的结点？例如，在图3.4（a）中重复
// 结点被删除之后，链表如图3.4（b）所示。

#include <iostream>
#include "List.h"
using namespace std;

void DeleteDuplication(ListNode** pHead)//注意有可能删除头结点，所以是**
{
    if (pHead == nullptr || *pHead == nullptr)
        return;

    ListNode* pPreNode = nullptr;//用来存储当前最后一个不删的节点
    ListNode* pNode = *pHead;//用来存储下一个待检测的节点
    while (pNode != nullptr)
    {
        ListNode *pNext = pNode->m_pNext;
        bool needDelete = false;
        if (pNext != nullptr && pNext->m_nValue == pNode->m_nValue)//开始检测是否删除
            needDelete = true;

        if (!needDelete)//不要删除的话就往下走
        {
            pPreNode = pNode;
            pNode = pNode->m_pNext;
        }
        else//要删除的话，看看删几个
        {
            int value = pNode->m_nValue;//记住要删的数
            ListNode* pToBeDel = pNode;
            while (pToBeDel != nullptr && pToBeDel->m_nValue == value)//满足
            {
                pNext = pToBeDel->m_pNext;

                delete pToBeDel;//删
                pToBeDel = nullptr;

                pToBeDel = pNext;
            }

            if (pPreNode == nullptr)//要是一直在删头结点，就把这个给头结点
                *pHead = pNext;
            else
                pPreNode->m_pNext = pNext;
            pNode = pNext;
        }
    }
}

// ====================测试代码====================
void Test(const char* testName, ListNode** pHead, int* expectedValues, int expectedLength)
{
    if (testName != nullptr)
        printf("%s begins: ", testName);

    DeleteDuplication(pHead);

    int index = ;
    ListNode* pNode = *pHead;
    while (pNode != nullptr && index < expectedLength)
    {
        if (pNode->m_nValue != expectedValues[index])
            break;

        pNode = pNode->m_pNext;
        index++;
    }

    if (pNode == nullptr && index == expectedLength)
        printf("Passed.\n");
    else
        printf("FAILED.\n");
}

// 某些结点是重复的
void Test1()
{
    ListNode* pNode1 = CreateListNode();
    ListNode* pNode2 = CreateListNode();
    ListNode* pNode3 = CreateListNode();
    ListNode* pNode4 = CreateListNode();
    ListNode* pNode5 = CreateListNode();
    ListNode* pNode6 = CreateListNode();
    ListNode* pNode7 = CreateListNode();

    ConnectListNodes(pNode1, pNode2);
    ConnectListNodes(pNode2, pNode3);
    ConnectListNodes(pNode3, pNode4);
    ConnectListNodes(pNode4, pNode5);
    ConnectListNodes(pNode5, pNode6);
    ConnectListNodes(pNode6, pNode7);

    ListNode* pHead = pNode1;

    int expectedValues[] = { , ,  };
    Test("Test1", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));

    DestroyList(pHead);
}

// 没有重复的结点
void Test2()
{
    ListNode* pNode1 = CreateListNode();
    ListNode* pNode2 = CreateListNode();
    ListNode* pNode3 = CreateListNode();
    ListNode* pNode4 = CreateListNode();
    ListNode* pNode5 = CreateListNode();
    ListNode* pNode6 = CreateListNode();
    ListNode* pNode7 = CreateListNode();

    ConnectListNodes(pNode1, pNode2);
    ConnectListNodes(pNode2, pNode3);
    ConnectListNodes(pNode3, pNode4);
    ConnectListNodes(pNode4, pNode5);
    ConnectListNodes(pNode5, pNode6);
    ConnectListNodes(pNode6, pNode7);

    ListNode* pHead = pNode1;

    int expectedValues[] = { , , , , , ,  };
    Test("Test2", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));

    DestroyList(pHead);
}

// 除了一个结点之外其他所有结点的值都相同
void Test3()
{
    ListNode* pNode1 = CreateListNode();
    ListNode* pNode2 = CreateListNode();
    ListNode* pNode3 = CreateListNode();
    ListNode* pNode4 = CreateListNode();
    ListNode* pNode5 = CreateListNode();
    ListNode* pNode6 = CreateListNode();
    ListNode* pNode7 = CreateListNode();

    ConnectListNodes(pNode1, pNode2);
    ConnectListNodes(pNode2, pNode3);
    ConnectListNodes(pNode3, pNode4);
    ConnectListNodes(pNode4, pNode5);
    ConnectListNodes(pNode5, pNode6);
    ConnectListNodes(pNode6, pNode7);

    ListNode* pHead = pNode1;

    int expectedValues[] = {  };
    Test("Test3", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));

    DestroyList(pHead);
}

// 所有结点的值都相同
void Test4()
{
    ListNode* pNode1 = CreateListNode();
    ListNode* pNode2 = CreateListNode();
    ListNode* pNode3 = CreateListNode();
    ListNode* pNode4 = CreateListNode();
    ListNode* pNode5 = CreateListNode();
    ListNode* pNode6 = CreateListNode();
    ListNode* pNode7 = CreateListNode();

    ConnectListNodes(pNode1, pNode2);
    ConnectListNodes(pNode2, pNode3);
    ConnectListNodes(pNode3, pNode4);
    ConnectListNodes(pNode4, pNode5);
    ConnectListNodes(pNode5, pNode6);
    ConnectListNodes(pNode6, pNode7);

    ListNode* pHead = pNode1;

    Test("Test4", &pHead, nullptr, );

    DestroyList(pHead);
}

// 所有结点都成对出现
void Test5()
{
    ListNode* pNode1 = CreateListNode();
    ListNode* pNode2 = CreateListNode();
    ListNode* pNode3 = CreateListNode();
    ListNode* pNode4 = CreateListNode();
    ListNode* pNode5 = CreateListNode();
    ListNode* pNode6 = CreateListNode();
    ListNode* pNode7 = CreateListNode();
    ListNode* pNode8 = CreateListNode();

    ConnectListNodes(pNode1, pNode2);
    ConnectListNodes(pNode2, pNode3);
    ConnectListNodes(pNode3, pNode4);
    ConnectListNodes(pNode4, pNode5);
    ConnectListNodes(pNode5, pNode6);
    ConnectListNodes(pNode6, pNode7);
    ConnectListNodes(pNode7, pNode8);

    ListNode* pHead = pNode1;

    Test("Test5", &pHead, nullptr, );

    DestroyList(pHead);
}

// 除了两个结点之外其他结点都成对出现
void Test6()
{
    ListNode* pNode1 = CreateListNode();
    ListNode* pNode2 = CreateListNode();
    ListNode* pNode3 = CreateListNode();
    ListNode* pNode4 = CreateListNode();
    ListNode* pNode5 = CreateListNode();
    ListNode* pNode6 = CreateListNode();
    ListNode* pNode7 = CreateListNode();
    ListNode* pNode8 = CreateListNode();

    ConnectListNodes(pNode1, pNode2);
    ConnectListNodes(pNode2, pNode3);
    ConnectListNodes(pNode3, pNode4);
    ConnectListNodes(pNode4, pNode5);
    ConnectListNodes(pNode5, pNode6);
    ConnectListNodes(pNode6, pNode7);
    ConnectListNodes(pNode7, pNode8);

    ListNode* pHead = pNode1;

    int expectedValues[] = { ,  };
    Test("Test6", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));

    DestroyList(pHead);
}

// 链表中只有两个不重复的结点
void Test7()
{
    ListNode* pNode1 = CreateListNode();
    ListNode* pNode2 = CreateListNode();

    ConnectListNodes(pNode1, pNode2);

    ListNode* pHead = pNode1;

    int expectedValues[] = { ,  };
    Test("Test7", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));

    DestroyList(pHead);
}

// 结点中只有一个结点
void Test8()
{
    ListNode* pNode1 = CreateListNode();

    ConnectListNodes(pNode1, nullptr);

    ListNode* pHead = pNode1;

    int expectedValues[] = {  };
    Test("Test8", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));

    DestroyList(pHead);
}

// 结点中只有两个重复的结点
void Test9()
{
    ListNode* pNode1 = CreateListNode();
    ListNode* pNode2 = CreateListNode();

    ConnectListNodes(pNode1, pNode2);

    ListNode* pHead = pNode1;

    Test("Test9", &pHead, nullptr, );

    DestroyList(pHead);
}

// 空链表
void Test10()
{
    ListNode* pHead = nullptr;

    Test("Test10", &pHead, nullptr, );
}

int main(int argc, char* argv[])
{
    Test1();
    Test2();
    Test3();
    Test4();
    Test5();
    Test6();
    Test7();
    Test8();
    Test9();
    Test10();
    system("pause");
    return ;
}