/*******************************************************************
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（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 <cstdio>
#include "list.h"
void DeleteDuplicationAnswer(ListNode** pHead)
{
if (pHead == nullptr || *pHead == nullptr)
return;
ListNode* pPreNode = nullptr;
ListNode* pNode = *pHead;
while (pNode != nullptr)
{
ListNode *pNext = pNode->m_pNext;
bool needDelete = false;
if (pNext != nullptr && pNext->m_nValue == pNode->m_nValue)
needDelete = true;
if (!needDelete)
{
pPreNode = pNode;
pNode = pNode->m_pNext;
}
else
{
int value = pNode->m_nValue;
ListNode* pToBeDel = pNode;
while (pToBeDel != nullptr && pToBeDel->m_nValue == value)
{
pNext = pToBeDel->m_pNext;
delete pToBeDel;
pToBeDel = nullptr;
pToBeDel = pNext;
}
if (pPreNode == nullptr)
*pHead = pNext;
else
pPreNode->m_pNext = pNext;
pNode = pNext;
}
}
}
/*
1. 头节点可能与后面的节点重复，头节点可能被删除
2. 从头遍历整个链表，如果当前节点和下一节点的值相同，删除
3. 删除后，当前节点的前一节点和后面值比当前节点的值大的节点相连
如果头节点为空，返回
while(当前节点不为空)
{
如果找到重复节点，删除标志位为真
删除标志为假
{
循环下一节点
}
删除标志为真：
{
删掉连续的重复节点，判断是不是空，防止到了尾节点
如果是从头节点开始重复了，重置新的头节点指针
如果不是的话，前一节点连接不重复的节点
重置当前节点的位置为pNext
}
}
*/
void DeleteDuplication(ListNode** pHead)
{
if (pHead == nullptr || *pHead == nullptr)
return;
/*如果头节点不是重复节点，那么链表的头节点地址是不变的，中间内容会变*/
/*pNode的作用是遍历链表，减掉重复节点，再把断的链表连起来*/
/*只要有了链表头节点地址就可以遍历整个链表，有了地址就可以访问和修改里面内容，这样是有效的*/
ListNode *pNode = *pHead;
ListNode *pPre = nullptr;
/*终止条件是pNode==nullptr,这时*pHead并没有变！！！*/
while (pNode != nullptr)
{
bool need_delete = false;
ListNode *pNext = pNode->m_pNext;
// need delete conditions
if (pNode->m_pNext != nullptr &&/* 如果只有一个节点，则下一节点没有值*/
pNode->m_nValue == pNext->m_nValue)
need_delete = true;
// do not need delete
if (!need_delete)
{
pPre = pNode;
pNode = pNode->m_pNext;
}
else//need delete
{
ListNode *pToBeDeleted = pNode;
int value = pNode->m_nValue;
while (pToBeDeleted != nullptr && pToBeDeleted->m_nValue == value)
{
pNext = pToBeDeleted->m_pNext;
delete pToBeDeleted;
pToBeDeleted = nullptr; //？？
pToBeDeleted = pNext;
}
/*从头节点开始就重复了,还没来得及给Pre节点赋值*/
if (pPre == nullptr)
*pHead = pToBeDeleted;//重置头节点指针，不能使用pNode,作为null退出
else
{
pPre->m_pNext = pToBeDeleted;
}
/* 1 1 1 4 5 5*/
pNode = pToBeDeleted;
/*
pNode和pHead作用是不同的，pHead记录头节点地址，有它可以访问所有节点
pNode相当于迭代器，遍历每一节点，执行删除和连接操作。
*/
}
}
}
// ====================测试代码====================
void Test(char* testName, ListNode** pHead, int* expectedValues, int expectedLength)
{
if (testName != nullptr)
printf("%s begins: ", testName);
DeleteDuplication(pHead);
int index = 0;
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(1);
ListNode* pNode2 = CreateListNode(2);
ListNode* pNode3 = CreateListNode(3);
ListNode* pNode4 = CreateListNode(3);
ListNode* pNode5 = CreateListNode(4);
ListNode* pNode6 = CreateListNode(4);
ListNode* pNode7 = CreateListNode(5);
ConnectListNodes(pNode1, pNode2);
ConnectListNodes(pNode2, pNode3);
ConnectListNodes(pNode3, pNode4);
ConnectListNodes(pNode4, pNode5);
ConnectListNodes(pNode5, pNode6);
ConnectListNodes(pNode6, pNode7);
ListNode* pHead = pNode1;
int expectedValues[] = { 1, 2, 5 };
Test("Test1", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));
DestroyList(pHead);
}
// 没有重复的结点
void Test2()
{
ListNode* pNode1 = CreateListNode(1);
ListNode* pNode2 = CreateListNode(2);
ListNode* pNode3 = CreateListNode(3);
ListNode* pNode4 = CreateListNode(4);
ListNode* pNode5 = CreateListNode(5);
ListNode* pNode6 = CreateListNode(6);
ListNode* pNode7 = CreateListNode(7);
ConnectListNodes(pNode1, pNode2);
ConnectListNodes(pNode2, pNode3);
ConnectListNodes(pNode3, pNode4);
ConnectListNodes(pNode4, pNode5);
ConnectListNodes(pNode5, pNode6);
ConnectListNodes(pNode6, pNode7);
ListNode* pHead = pNode1;
int expectedValues[] = { 1, 2, 3, 4, 5, 6, 7 };
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(1);
ListNode* pNode2 = CreateListNode(1);
ListNode* pNode3 = CreateListNode(1);
ListNode* pNode4 = CreateListNode(1);
ListNode* pNode5 = CreateListNode(1);
ListNode* pNode6 = CreateListNode(1);
ListNode* pNode7 = CreateListNode(2);
ConnectListNodes(pNode1, pNode2);
ConnectListNodes(pNode2, pNode3);
ConnectListNodes(pNode3, pNode4);
ConnectListNodes(pNode4, pNode5);
ConnectListNodes(pNode5, pNode6);
ConnectListNodes(pNode6, pNode7);
ListNode* pHead = pNode1;
int expectedValues[] = { 2 };
Test("Test3", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));
DestroyList(pHead);
}
// 所有结点的值都相同
void Test4()
{
ListNode* pNode1 = CreateListNode(1);
ListNode* pNode2 = CreateListNode(1);
ListNode* pNode3 = CreateListNode(1);
ListNode* pNode4 = CreateListNode(1);
ListNode* pNode5 = CreateListNode(1);
ListNode* pNode6 = CreateListNode(1);
ListNode* pNode7 = CreateListNode(1);
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, 0);
DestroyList(pHead);
}
// 所有结点都成对出现
void Test5()
{
ListNode* pNode1 = CreateListNode(1);
ListNode* pNode2 = CreateListNode(1);
ListNode* pNode3 = CreateListNode(2);
ListNode* pNode4 = CreateListNode(2);
ListNode* pNode5 = CreateListNode(3);
ListNode* pNode6 = CreateListNode(3);
ListNode* pNode7 = CreateListNode(4);
ListNode* pNode8 = CreateListNode(4);
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, 0);
DestroyList(pHead);
}
// 除了两个结点之外其他结点都成对出现
void Test6()
{
ListNode* pNode1 = CreateListNode(1);
ListNode* pNode2 = CreateListNode(1);
ListNode* pNode3 = CreateListNode(2);
ListNode* pNode4 = CreateListNode(3);
ListNode* pNode5 = CreateListNode(3);
ListNode* pNode6 = CreateListNode(4);
ListNode* pNode7 = CreateListNode(5);
ListNode* pNode8 = CreateListNode(5);
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[] = { 2, 4 };
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(1);
ListNode* pNode2 = CreateListNode(2);
ConnectListNodes(pNode1, pNode2);
ListNode* pHead = pNode1;
int expectedValues[] = { 1, 2 };
Test("Test7", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));
DestroyList(pHead);
}
// 结点中只有一个结点
void Test8()
{
ListNode* pNode1 = CreateListNode(1);
ConnectListNodes(pNode1, nullptr);
ListNode* pHead = pNode1;
int expectedValues[] = { 1 };
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(1);
ListNode* pNode2 = CreateListNode(1);
ConnectListNodes(pNode1, pNode2);
ListNode* pHead = pNode1;
Test("Test9", &pHead, nullptr, 0);
DestroyList(pHead);
}
// 空链表
void Test10()
{
ListNode* pHead = nullptr;
Test("Test10", &pHead, nullptr, 0);
}
int main(int argc, char* argv[])
{
//Test1();
Test2();
//Test3();
//Test4();
//Test5();
//Test6();
//Test7();
//Test8();
//Test9();
//Test10();
return 0;
}
/*******************************************************************
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
//==================================================================
#include "list.h"
#include <stdio.h>
#include <stdlib.h>
ListNode* CreateListNode(int value)
{
ListNode* pNode = new ListNode();
pNode->m_nValue = value;
pNode->m_pNext = nullptr;
return pNode;
}
void ConnectListNodes(ListNode* pCurrent, ListNode* pNext)
{
if(pCurrent == nullptr)
{
printf("Error to connect two nodes.\n");
exit(1);
}
pCurrent->m_pNext = pNext;
}
void PrintListNode(ListNode* pNode)
{
if(pNode == nullptr)
{
printf("The node is nullptr\n");
}
else
{
printf("The key in node is %d.\n", pNode->m_nValue);
}
}
void PrintList(ListNode* pHead)
{
printf("PrintList starts.\n");
ListNode* pNode = pHead;
while(pNode != nullptr)
{
printf("%d\t", pNode->m_nValue);
pNode = pNode->m_pNext;
}
printf("\nPrintList ends.\n");
}
void DestroyList(ListNode* pHead)
{
ListNode* pNode = pHead;
while(pNode != nullptr)
{
pHead = pHead->m_pNext;
delete pNode;
pNode = pHead;
}
}
void AddToTail(ListNode** pHead, int value)
{
ListNode* pNew = new ListNode();
pNew->m_nValue = value;
pNew->m_pNext = nullptr;
if(*pHead == nullptr)
{
*pHead = pNew;
}
else
{
ListNode* pNode = *pHead;
while(pNode->m_pNext != nullptr)
pNode = pNode->m_pNext;
pNode->m_pNext = pNew;
}
}
void RemoveNode(ListNode** pHead, int value)
{
if(pHead == nullptr || *pHead == nullptr)
return;
ListNode* pToBeDeleted = nullptr;
if((*pHead)->m_nValue == value)
{
pToBeDeleted = *pHead;
*pHead = (*pHead)->m_pNext;
}
else
{
ListNode* pNode = *pHead;
while(pNode->m_pNext != nullptr && pNode->m_pNext->m_nValue != value)
pNode = pNode->m_pNext;
if(pNode->m_pNext != nullptr && pNode->m_pNext->m_nValue == value)
{
pToBeDeleted = pNode->m_pNext;
pNode->m_pNext = pNode->m_pNext->m_pNext;
}
}
if(pToBeDeleted != nullptr)
{
delete pToBeDeleted;
pToBeDeleted = nullptr;
}
}
/*******************************************************************
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
//==================================================================
struct ListNode
{
int m_nValue;
ListNode* m_pNext;
};
__declspec( dllexport ) ListNode* CreateListNode(int value);
__declspec( dllexport ) void ConnectListNodes(ListNode* pCurrent, ListNode* pNext);
__declspec( dllexport ) void PrintListNode(ListNode* pNode);
__declspec( dllexport ) void PrintList(ListNode* pHead);
__declspec( dllexport ) void DestroyList(ListNode* pHead);
__declspec( dllexport ) void AddToTail(ListNode** pHead, int value);
__declspec( dllexport ) void RemoveNode(ListNode** pHead, int value);
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