题解 | #链表中的节点每k个一组翻转#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     * 
     * @param head ListNode类 
     * @param k int整型 
     * @return ListNode类
     */
    public ListNode reverseKGroup (ListNode head, int k) {
        // write code here
        if(head == null) return head;
        List<ListNode> list=new ArrayList<>();
        ListNode curr=head;
        while(curr != null){
            list.add(curr);
            curr=curr.next;
        }
        for(int i=0;i+k<=list.size();i+=k){
            for(int j=i;j<i+k/2;j++){
                ListNode temp=list.get(j);
                list.set(j,list.get(k+2*i-1-j));
                list.set(k+2*i-1-j,temp);
            }
        }
        for(int i=0;i<list.size()-1;i++){
            list.get(i).next=list.get(i+1);
        }
        list.get(list.size()-1).next=null;
        return list.get(0);
    }
}