leetcode25.k个一组翻转链表

思路源自

【力扣hot100】【LeetCode 25】k个一组翻转链表｜虚拟节点的应用

 

/*** 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 reverseKGroup(ListNode head, int k) {ListNode dummyHead = new ListNode(0, head);ListNode cur = dummyHead;while (true) {ListNode groupPre = cur;int kth = k;while (cur != null && kth > 0) {cur=cur.next;kth--;}if (cur == null) {break;} else {ListNode groupNext = cur.next;cur = groupPre.next;ListNode pre = groupNext;while (cur != groupNext) {ListNode temp = cur.next;cur.next = pre;pre=cur;cur = temp;}cur = groupPre.next;groupPre.next = pre;}}return dummyHead.next;}
}