leetcode 24. Swap Nodes in Pairs | 24. 两两交换链表中的节点（Java）

深藏阁楼爱情的钟 2022-08-30 05:16 23阅读 0赞

## 题目 ##

[https://leetcode.com/problems/swap-nodes-in-pairs/][https_leetcode.com_problems_swap-nodes-in-pairs]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]

## 题解 ##

两两翻转，链表题 so easy  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_1_color_FFFFFF_t_70]

/** * 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) { 
            if (head == null || head.next == null) return head;
            ListNode L = head;
            ListNode R = head.next;
            head = head.next;
            while (true) { 
                L.next = R.next;
                R.next = L;
                if (L.next == null || L.next.next == null) break;
                ListNode pre = L;
                L = L.next;
                R = L.next;
                pre.next = R;
            }
            return head;
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]

[https_leetcode.com_problems_swap-nodes-in-pairs]: https://leetcode.com/problems/swap-nodes-in-pairs/
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_1_color_FFFFFF_t_70]: /images/20220829/a8cb18ccb2d3475a9f0add21cd387fe1.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]: /images/20220829/626c24d050a142be9e65f447870ee0d4.png