leetcode 1721. Swapping Nodes in a Linked List | 1721. 交换链表中的节点（Java）

灰太狼 2022-08-30 05:16 18阅读 0赞

## 题目 ##

[https://leetcode.com/problems/swapping-nodes-in-a-linked-list/][https_leetcode.com_problems_swapping-nodes-in-a-linked-list]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]

## 题解 ##

思路很简单：找到左节点，找到右节点，最后交换左右节点的 value 即可。

/** * 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 swapNodes(ListNode head, int k) { 
            int length = 0;
            ListNode node = head;
            while (node != null) { 
                length++;
                node = node.next;
            }
            if (length <= 1) return head;
    
            ListNode L = head;
            int left = k - 1;
            while (left > 0) { 
                L = L.next;
                left--;
            }
    
            ListNode R = head;
            int right = length - k;
            while (right > 0) { 
                R = R.next;
                right--;
            }
            // 题目说swapping the values of the node，所以值交换即可，不需要交换节点
            int t = L.val;
            L.val = R.val;
            R.val = t;
            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_swapping-nodes-in-a-linked-list]: https://leetcode.com/problems/swapping-nodes-in-a-linked-list/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]: /images/20220829/76e2e1fd19974be19e8a8860a488face.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]: /images/20220829/f86846608dce47c0bfaeb5d7998b405f.png