给你链表的头节点 head 和一个整数 k 。
交换 链表正数第 k 个节点和倒数第 k 个节点的值后,返回链表的头节点(链表 从 1 开始索引)。
示例 1:
输入:head = [1,2,3,4,5], k = 2
输出:[1,4,3,2,5]
示例 2:
输入:head = [7,9,6,6,7,8,3,0,9,5], k = 5
输出:[7,9,6,6,8,7,3,0,9,5]
示例 3:
输入:head = [1], k = 1
输出:[1]
示例 4:
输入:head = [1,2], k = 1
输出:[2,1]
示例 5:
输入:head = [1,2,3], k = 2
输出:[1,2,3]
提示:
链表中节点的数目是 n
1 <= k <= n <= 105
0 <= Node.val <= 100
思路:两个指针找到以后交换值即可。
‘
/*** 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) {ListNode cur = head;ListNode first = head;ListNode last = head;int count = 1;while (cur.next != null) {// 找到正数第k个节点if (count < k) {first = first.next;// 找到倒数第k个节点} else {last = last.next;}count++;cur = cur.next;}// 交换正数第k个节点和倒数第k个节点的值count = first.val;first.val = last.val;last.val = count;return head;}
}