如何实现单链表交换任意两个元素（不包括头结点）

对于单链表而言，假设交换A、B两个节点，那么需要交换A与B的next指针以及A、B直接前驱的next指针。

需要注意特殊情况：1、当A与B相邻时：A->next = B;或者B->next = A;

　　　　　　　　　2、当A和B元素相同时，则没有必要交换。

　　　　　　　　　3、A与B有一个节点是头结点，不需要交换。

#include <iostream>
#include <algorithm>
#include "string.h"
#include "stdio.h"
#include <vector>
#include <deque>
#include<stack>
using namespace std;

struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};
class List{
public:

    ListNode* CreatList(int* arr,int len)
    {
        int val;
        ListNode* pHead = new ListNode(arr[0]);
        ListNode* pCurrent=NULL;
        ListNode* rear = pHead;
        int count = 1;
        while(count<len)
        {
            ListNode* pCurrent = new ListNode(arr[count]);
            rear->next = pCurrent;
            rear = pCurrent;
            count++;
        }
        rear->next = NULL;
        return pHead;
    }
    void ShowList(ListNode* pHead)
    {
       while(pHead)
       {
           cout<<pHead->val<<" ";
           pHead = pHead->next;
       }
       cout<<endl;
    }
    ListNode* GetLastNode(ListNode* pHead)
    {
        ListNode* pNode = pHead;
        while(pNode->next!=NULL)
        {
            pNode=pNode->next;
        }
        return pNode;
    }
};
class Sort{
public:
    ListNode* changeList(ListNode* pHead,ListNode* pNode1,ListNode* pNode2)
    {
        if(pHead == NULL|| pNode1 == NULL || pNode2 == NULL)
            return pHead;
        //结点pNode1 等于pNode2
        if(pNode1->val == pNode2->val)
            return pHead;
        if(pNode1->next == pNode2)
        {
            ListNode* pre = FindPre(pHead,pNode1);
            if(pre == NULL)
                return pHead;
            pre->next = pNode2;
            pNode1->next = pNode2->next;
            pNode2->next = pNode1;
        }
        else if(pNode2->next == pNode1)
        {
            ListNode* pre = FindPre(pHead,pNode2);
            if(pre == NULL)
                return pHead;
            pre->next = pNode1;
            pNode2->next = pNode1->next;
            pNode1->next = pNode2;
        }
        else if(pNode1!=pNode2){
            ListNode* pre1 = FindPre(pHead,pNode1);
            ListNode* pre2 = FindPre(pHead,pNode2);
            ListNode* next1 = pNode1->next;
            ListNode* next2 = pNode2->next;
            pre1->next = pNode2;
            pNode2->next = next1;
            pre2->next = pNode1;
            pNode1->next = next2;
        }
        return pHead;
    }

    ListNode* FindPre(ListNode* pHead,ListNode* pNode)
    {
        ListNode* p = pHead;
        while(p)
        {
            if(p->next == pNode)
                return p;
            p = p->next;
        }
        return NULL;
    }

};
int array[7];
int n;
int number;
int first;
int second;
int main()
{
    cin>>n;

    for(int i=0;i<n;i++)
    {
        cin>>number;
        array[i]=number;
    }

    cin>>first;
    cin>>second;

    List list;
    Sort sort;
    ListNode* pHead1 = list.CreatList(array,sizeof(array)/sizeof(array[0]));
    ListNode* pNode1 = pHead1;
    ListNode* pNode2 = pHead1;
    for(int i=1;i<first;i++)
    {
        pNode1=pNode1->next;
    }
    cout<<pNode1->val<<endl;
    for(int i=1;i<second;i++)
    {
        pNode2 = pNode2->next;
    }
    cout<<pNode2->val<<endl;
    list.ShowList(pHead1);
    ListNode* p = sort.changeList(pHead1,pNode1,pNode2);
    //cout<<pEnd->val<<endl;
    list.ShowList(p);
    return 0;
}