24. Swap Nodes in Pairs

class Solution {
public:
ListNode* swapPairs(ListNode* head) {
ListNode *t1,*t2,*t3,*t4;
if(head==NULL||head->next==NULL)
    return head;                   
t4->next=t2->next;
t3=t2->next->next;
t2->next->next=t2;
t2->next=t3;
while(t2->next->next!=NULL)   
{
t1=t2->next;
t3=t2->next->next->next;
t2->next=t2->next->next;
t2->next->next=t1;
t1->next=t3;
t2=t1;
}
} 
}

 

Given a linked list, swap every two adjacent nodes and return its head.

For example,
Given 1->2->3->4, you should return the list as 2->1->4->3.

交换两个节点

思路：

很简单，就是三点

1、每次从交换节点的前一个节点开始

2、记录交换节点的后一个节点

3、交换两个节点

主要考察链表操作的逻辑