题目描述：
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：
我只想说递归大法好。
代码如下：
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
public class Solution {
public ListNode swapPairs(ListNode head) {
if (head == null)
return null;
if (head.next == null)
return head;
ListNode tmp = head.next;
ListNode forward = head.next.next;
tmp.next = head;
head.next = swapPairs(forward);
return tmp;
}
}
Java [leetcode 24]Swap Nodes in Pairs
原文：http://www.cnblogs.com/zihaowang/p/4506436.html