劍指offer-O(1)時間複雜度刪除單向鏈表指定結點

/*******************************************************************
Copyright(c) 2016, Tyrone Li
All rights reserved.
*******************************************************************/
// 作者:TyroneLi
//

/*
Q:
    給定單向鏈表的頭指針和一個結點指針，定義一個函數
    在O(1)時間複雜度內刪除。
S:
    常規的單向鏈表節點刪除操作都需要先遍歷得到要刪除節點的
    前一個結點，然後在刪除指定節點，但是這就需要O(n)時間複雜度，
    如果把給定節點的後一個結點的數據拷貝到指定節點，然後把指定節點
    後一個結點刪除，這就可以實現在O(1)時間複雜度內刪除指定節點。
*/

#include "../utils/List.h"
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>

/* 該實現基於一個基本的假設，也就是要刪除的結點確實在鏈表中 */
void deleteListNode_quick(ListNode**pHead, ListNode*pDeletedNode)
{
    if(pHead == nullptr || pDeletedNode == nullptr)
        return;
    
    if(pDeletedNode->m_pNext != nullptr){
        ListNode*pNext = pDeletedNode->m_pNext;
        pDeletedNode->m_nValue = pNext->m_nValue;
        pDeletedNode->m_pNext = pNext->m_pNext;
        delete pNext;
        pNext = nullptr;
    }else if(*pHead == pDeletedNode)
    {
        delete pDeletedNode;
        pDeletedNode = nullptr;
        *pHead = nullptr;
    }else{
        ListNode*pNode = *pHead;
        while(pNode->m_pNext != pDeletedNode)
            pNode = pNode->m_pNext;
        
        pNode->m_pNext = nullptr;
        delete pDeletedNode;
        pDeletedNode = nullptr;
    }
}

void test_1()
{
    std::cout << "one node in list delete first node" << std::endl;
    ListNode*pHead = createListNode(1);
    printList(pHead);
    deleteListNode_quick(&pHead, pHead);
    printList(pHead);
    std::cout << "===========================" << std::endl;
}

void test_2()
{
    std::cout << "multi node in list delete head node" << std::endl;
    ListNode*pHead = createListNode(1);
    ListNode*pHead2 = createListNode(2);
    connectListNodes(pHead, pHead2);
    printList(pHead);
    deleteListNode_quick(&pHead, pHead);
    printList(pHead);
    std::cout << "===========================" << std::endl;
}

void test_3()
{
    std::cout << "multi node in list, delete among node" << std::endl;
    ListNode*pHead = createListNode(1);
    ListNode*pHead2 = createListNode(2);
    ListNode*pHead3 = createListNode(3);
    connectListNodes(pHead, pHead2);
    connectListNodes(pHead2, pHead3);
    printList(pHead);
    deleteListNode_quick(&pHead, pHead2);
    printList(pHead);
    std::cout << "===========================" << std::endl;
}

void test_4()
{
    std::cout << "multi node in list, delete tail node" << std::endl;
    ListNode*pHead = createListNode(1);
    ListNode*pHead2 = createListNode(2);
    ListNode*pHead3 = createListNode(3);
    connectListNodes(pHead, pHead2);
    connectListNodes(pHead2, pHead3);
    printList(pHead);
    deleteListNode_quick(&pHead, pHead3);
    printList(pHead);
    std::cout << "===========================" << std::endl;
}

void test_5()
{
    std::cout << "test NULL list" << std::endl;
    ListNode*pHead = nullptr;
    printList(pHead);
    deleteListNode_quick(&pHead, pHead);
    printList(pHead);
    std::cout << "============================" << std::endl;
}

void test_deleteListNode_quick()
{
    test_1();
    test_2();
    test_3();
    test_4();
    test_5();
}

int main(int argc, char**argv)
{

    test_deleteListNode_quick();

    return 0;
}