剑指offer——链表

#include"stdio.h"
#include"stdlib.h"
#include"iostream"
using namespace std;

struct ListNode
{
    int m_Value;
    ListNode* m_pNext;
};

ListNode* CreateListNode(int value)
{
    ListNode* pNode=new ListNode();
    pNode->m_Value=value;
    pNode->m_pNext=nullptr;

    return pNode;
}

void ConnectListNodes(ListNode* pCurrent,ListNode* pNext)
{
    if(pCurrent==nullptr)
    {
        cout<<"Error to connect two nodes."<<endl;
        exit(1);
    }
    pCurrent->m_pNext=pNext;
}

void PrintListNode(ListNode* pNode)
{
    if(pNode==nullptr)
    {
        cout<<"The node is nullptr."<<endl;
    }
    else
    {
        cout<<"the value in node is: "<<pNode->m_Value<<endl;
    }
}

void PrintList(ListNode *pHead)
{
    cout<<"PrintList starts."<<endl;

    ListNode* pNode=pHead;
    while(pNode!=nullptr)
    {
        cout<<pNode->m_Value<<" ";
        pNode=pNode->m_pNext;
    }
    cout<<endl<<"PrintList ends."<<endl;
}

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* pNode=CreateListNode(value);
    if(pHead==nullptr || *pHead==nullptr)
    {
        *pHead=pNode;
    }
    else
    {
        ListNode* pTemp=*pHead;
        while(pTemp->m_pNext!=nullptr)
            pTemp=pTemp->m_pNext;
        pTemp->m_pNext=pNode;
    }
}

void RemoveNode(ListNode** pHead,int value)
{
    if(pHead == nullptr || *pHead == nullptr)
        return;

    ListNode* pToBeDeleted = nullptr;
    if((*pHead)->m_Value == value)
    {
        pToBeDeleted = *pHead;
        *pHead = (*pHead)->m_pNext;
    }
    else
    {
        ListNode* pNode = *pHead;
        while(pNode->m_pNext != nullptr && pNode->m_pNext->m_Value != value)
            pNode = pNode->m_pNext;

        if(pNode->m_pNext != nullptr && pNode->m_pNext->m_Value == value)
        {
            pToBeDeleted = pNode->m_pNext;
            pNode->m_pNext = pNode->m_pNext->m_pNext;
        }
    }

    if(pToBeDeleted != nullptr)
    {
        delete pToBeDeleted;
        pToBeDeleted = nullptr;//防止指正悬挂
    }
}
//O(1)复杂度
void DeleteNode(ListNode** pHead,ListNode* pToBeDeleted)
{
    if(*pHead==nullptr || pToBeDeleted==nullptr)
        return;
    if(pToBeDeleted->m_pNext!=nullptr)
    {
        ListNode* pNext=pToBeDeleted->m_pNext;
        pToBeDeleted->m_pNext=pNext->m_pNext;
        pToBeDeleted->m_Value=pNext->m_Value;
        delete pNext;
        pNext=nullptr;
    }
    else if(pToBeDeleted==*pHead)
    {
        delete pToBeDeleted;
        pToBeDeleted=nullptr;
        *pHead=nullptr;
    }
    else
    {
        ListNode* pNode=*pHead;
        while(pNode->m_pNext!=pToBeDeleted)
            pNode=pNode->m_pNext;
        pNode->m_pNext=nullptr;
        delete pToBeDeleted;
        pToBeDeleted=nullptr;
    }
}

ListNode* TheLastKthNode(ListNode* pHead,int k)
{
    if(pHead==nullptr || k<=0)
        return nullptr;
    ListNode* quickNode=pHead;
    ListNode* slowNode=pHead;
    int cnt=1;
    while(quickNode->m_pNext!=nullptr&&cnt<k)
    {
        quickNode=quickNode->m_pNext;
        ++cnt;
    }
    if(cnt<k)
        return nullptr;
    while(quickNode->m_pNext!=nullptr)
    {
        quickNode=quickNode->m_pNext;
        slowNode=slowNode->m_pNext;
    }
    return slowNode;
}

ListNode* MeetingNode(ListNode* pHead)
{
    if(pHead==nullptr)
        return nullptr;
    ListNode* quickNode=pHead;
    ListNode* slowNode=pHead;

    while(quickNode->m_pNext!=nullptr&&quickNode->m_pNext->m_pNext!=nullptr)
    {
        quickNode=quickNode->m_pNext->m_pNext;
        slowNode=slowNode->m_pNext;
        if(quickNode==slowNode)
            break;
    }
    if(quickNode!=slowNode)
    {
        return nullptr;
    }
    return slowNode;
}

ListNode* EntryNodeOfLoop(ListNode* pHead)
{
    ListNode* meetingNode=MeetingNode(pHead);
    if(meetingNode==nullptr)
        return nullptr;
    int nodesInLoop=1;
    ListNode* pTemp=meetingNode;
    while(pTemp->m_pNext!=meetingNode)
    {
        pTemp=pTemp->m_pNext;
        nodesInLoop++;
    }
    ListNode* quickNode=pHead;
    ListNode* slowNode=pHead;
    for(int i=0;i<nodesInLoop;i++)
        quickNode=quickNode->m_pNext;
    while(slowNode!=quickNode)
    {
        quickNode=quickNode->m_pNext;
        slowNode=slowNode->m_pNext;
    }
    return slowNode;
}