LeetCode 24 Swap Nodes in Pairs （交换相邻节点）

package leetcode_50;

/**
*
* @author pengfei_zheng
* 交换相邻节点
*/
public class Solution24 {
public class ListNode {
int val;
ListNode next;
ListNode(int x) { val = x; }
}

public ListNode swapPairs(ListNode head) {
if ((head == null)||(head.next == null))
return head;
ListNode n = head.next;
head.next = swapPairs(head.next.next);
n.next = head;
return n;
}
}