题解 | #删除有序链表中重复的元素-II#

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
        if(head == null || head.next ==null){
            return head;
        }

        ListNode dummy = new ListNode(-1);
        dummy.next = head;

        ListNode pre = dummy;

        while(pre.next!=null&&pre.next.next!=null){
            if(pre.next.val == pre.next.next.val){
                int temp = pre.next.val;
                while(pre.next != null && pre.next.val == temp){
                    pre.next = pre.next.next;
                }
            
            }else{
                pre = pre.next;
            }
        }
        return dummy.next;
    }
}