题解 | #牛群排列去重# 递归版本

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 deleteDuplicates (ListNode head) {
        // write code here
        // 递归
        if (head == null || head.next == null) return head; 
        head.next = deleteDuplicates(head.next);

        if (head.next.val == head.val)
            head.next = head.next.next;

        return head;
    }
}