leetcode Reverse Nodes in k-Group

题目链接

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
     public ListNode reverseKGroup(ListNode head, int k) {
        ListNode newHead=new ListNode(1);
        ListNode result=newHead;

        ListNode pointer=head;
        while(pointer!=null)
        {
            ListNode end=pointer;
            for(int i=1;i<k&&end!=null;i++)
            {
                end=end.next;
            }
            if(end==null)
            {
                newHead.next=pointer;
                break;
            }

            ListNode nextPoin=end.next;

            end.next=null;
            newHead.next=reverse(pointer);
            newHead=pointer;
            pointer=nextPoin;
        }

        return result.next;
    }

    public ListNode reverse(ListNode toReverse)
    {

        ListNode result=null;
        while(toReverse!=null)
        {
            ListNode temp=toReverse.next;


            toReverse.next=result;
            result=toReverse;
            toReverse=temp;


        }
        return result;


    }
}