LeetCode : Swap Nodes in Pairs [java]

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.

思路：纯链表操作，使用额外节点记录"指针"，主要需要记录的是：当前交换的两个节点，两个节点后的节点（如果有的话）以及构建新链表的"指针".

/**
 * 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) {
		ListNode myHead = new ListNode(-1);
		ListNode myPointer = myHead;
		while (head != null) {
			ListNode next2 = head.next;
			if (next2 == null) {
				myPointer.next = head;
				break;
			} else {
				next2 = next2.next;
				ListNode qian = head;
				ListNode hou = head.next;
				qian.next = hou.next;
				hou.next = qian;
				myPointer.next = hou;
				myPointer = myPointer.next.next;
				head = next2;
			}
		}
		return myHead.next;
    }
}