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;
}