LeetCode 1721. Swapping Nodes in a Linked List

2022-06-16 03:31:06 阅读：194 来源： 互联网

标签：head ListNode Swapping val runner list List next LeetCode

原题链接在这里：https://leetcode.com/problems/swapping-nodes-in-a-linked-list/

题目：

You are given the head of a linked list, and an integer k.

Return the head of the linked list after swapping the values of the kth node from the beginning and the kth node from the end (the list is 1-indexed).

Example 1:

Input: head = [1,2,3,4,5], k = 2
Output: [1,4,3,2,5]

Example 2:

Input: head = [7,9,6,6,7,8,3,0,9,5], k = 5
Output: [7,9,6,6,8,7,3,0,9,5]

Constraints:

The number of nodes in the list is n.
1 <= k <= n <= 105
0 <= Node.val <= 100

题解：

Move the runner k times, and have a mark. This is the kth node from the beginning.

Now move both walker and runner until runner == null. Now walker is the kth ndoe from the end.

Note: check k is larger than list length.

Time Complexity: O(n). n is the length of list.

Space: O(1).

AC Java:

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     int val;
 5  *     ListNode next;
 6  *     ListNode() {}
 7  *     ListNode(int val) { this.val = val; }
 8  *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 9  * }
10  */
11 class Solution {
12     public ListNode swapNodes(ListNode head, int k) {
13         if(head == null){
14             return head;
15         }
16         
17         ListNode dummy = new ListNode(-1);
18         dummy.next = head;
19         ListNode runner = dummy;
20         ListNode walker = dummy;
21         while(runner.next != null && k > 0){
22             runner = runner.next;
23             k--;
24         }
25         
26         if(k > 0){
27             return head;
28         }
29         
30         ListNode mark = runner;
31         while(runner != null){
32             runner = runner.next;
33             walker = walker.next;
34         }
35         
36         int temp = walker.val;
37         walker.val = mark.val;
38         mark.val = temp;
39         return dummy.next;
40     }
41 }

类似Remove Nth Node From End of List.

标签：head,ListNode,Swapping,val,runner,list,List,next,LeetCode
来源： https://www.cnblogs.com/Dylan-Java-NYC/p/16380564.html

本站声明： 1. iCode9 技术分享网（下文简称本站）提供的所有内容，仅供技术学习、探讨和分享；
2. 关于本站的所有留言、评论、转载及引用，纯属内容发起人的个人观点，与本站观点和立场无关；
3. 关于本站的所有言论和文字，纯属内容发起人的个人观点，与本站观点和立场无关；
4. 本站文章均是网友提供，不完全保证技术分享内容的完整性、准确性、时效性、风险性和版权归属；如您发现该文章侵犯了您的权益，可联系我们第一时间进行删除；
5. 本站为非盈利性的个人网站，所有内容不会用来进行牟利，也不会利用任何形式的广告来间接获益，纯粹是为了广大技术爱好者提供技术内容和技术思想的分享性交流网站。

ICode9

LeetCode 1721. Swapping Nodes in a Linked List