题解 | #牛群排列去重#

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) {
        //解决边界问题
        if (head == null || head.next == null) {
            return head;

        }

        ListNode pre = head;
        ListNode cur = head.next;

        while (cur != null) {
            if (pre.val == cur.val) {
                pre.next = cur.next;
                cur = cur.next;
            } else {
                pre = cur;
                cur = cur.next;
            }
        }
        return head;
    }
}