题解 | #反转链表#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

/**
* 使用递归的方式解决
**/
public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    public ListNode ReverseList (ListNode head) {
        // write code here
        if(head == null){
            return null;
        }
        ListNode cur = head;
        while(cur.next != null){
            cur = cur.next;
        }
        head = reverse(head);
        head.next = null;
        return cur;

    }

    public ListNode reverse(ListNode cur){
        if(cur.next == null){
            return cur;
        }else{
            ListNode next = reverse(cur.next);
            next.next = cur;
            return cur;
        }
    }
}