题解 | #反转链表#

import java.util.*;

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

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
        return recursion(null, head);
    }


    ListNode recursion(ListNode pre, ListNode next){
        if(next == null){
            return pre;
        }
        ListNode temp = next.next;
        next.next = pre;
        pre = next;
        next = temp;
        return recursion(pre, next);
    }
    
}