题解 | #两两交换链表的节点#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param head ListNode类
     * @return ListNode类
     */
    public ListNode swapLinkedPair (ListNode head) {
        // write code here
        if (head == null || head.next == null)
            return head;
        ListNode lnRtn = head.next;
        ListNode lnQTmp = new ListNode(0);
        while (head != null && head.next != null) {
            lnQTmp.next = head.next;
            lnQTmp = lnQTmp.next;
            ListNode lnTmp = head;
            head = lnQTmp.next;
            lnQTmp.next = lnTmp;
            lnTmp.next = head;
            lnQTmp = lnTmp;
        }
        return lnRtn;
    }
}