【Leetcode】Swap Nodes in Pairs

题目：

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.

Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.

解题思路：本题较简单，做3次指针变换就可以完成一轮交换。

代码：

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *swapPairs(ListNode *head) {
        ListNode *Zero;
        ListNode *First=head,*Second;
        ListNode Forehead(0);
        if(head==NULL||head->next==NULL)return head;
        Zero=&Forehead;
        while(First!=NULL){
            Second=First->next;
            if(Second!=NULL){
                First->next=Second->next;
                Second->next=First;
                Zero->next=Second;
                Zero=First;
                First=First->next;
            }else{
                break;
            }
        }
        return Forehead.next;
    }
};

【Leetcode】Swap Nodes in Pairs,布布扣,bubuko.com

【Leetcode】Swap Nodes in Pairs

原文：http://blog.csdn.net/ussam/article/details/21638233