链表系列一＞ K 个一组翻转链表

题目：

链接: link

解析：

代码：

/*** 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 {/**prev: 用来头插tmp: 每次头插前记录一下，好进行下一次头插*/public ListNode reverseKGroup(ListNode head, int k) {ListNode cur = head;int n = 0;while(cur != null){cur = cur.next;n++;}n = n / k;//统计需要翻转链表几次cur = head;ListNode newHead = new ListNode(0);ListNode prev = newHead;for(int i = 0; i < n; i++){ListNode tmp = cur;for(int j = 0; j < k; j++){ListNode next = cur.next;cur.next = prev.next;prev.next = cur;cur = next; }prev = tmp;}//把后面不需要逆序的连接上prev.next = cur; return newHead.next;}
}