思路

定义一个指针cur,   先指向头节点，

1.判断后一个节点是否为空，不为空则交换值，

2.指针向后走两次

代码

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode swapPairs(ListNode head) {
  ListNode cur = head;
            while (cur != null&&cur.next!=null) {
                    int temp=cur.val;
                    cur.val=cur.next.val;
                    cur.next.val=temp;
                    cur = cur.next;
                    cur = cur.next;
            }

            return head;
    }
}

记录

总结