// 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 <iostream>
#include "List.h"void DeleteNode(ListNode** pListHead, ListNode* pToBeDeleted)
{if (!pListHead || !pToBeDeleted)return;// 第一种情况：要删除的结点不是尾结点if (pToBeDeleted->m_pNext != nullptr){ListNode* pNext = pToBeDeleted->m_pNext;//得到待删除节点的下一个节点pToBeDeleted->m_nValue = pNext->m_nValue;//将该节点的值和地址给覆盖待删除节点pToBeDeleted->m_pNext = pNext->m_pNext;delete pNext;//删除这个替罪羊pNext = nullptr;}// 第二种情况：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;//注意吧头结点置空
    }// 第三种情况：链表中有多个结点，删除尾结点else{ListNode* pNode = *pListHead;while (pNode->m_pNext != pToBeDeleted)//只能通过顺序查找并删除了
        {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);//注意这个函数的输入
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();system("pause");return 0;
}