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;
            ListNode cur = head;

            while(cur != null){
                boolean flag = false;

                while(cur.next != null && cur.val == cur.next.val){
                    cur =  cur.next;
                    flag = true;
                }

                if( flag){
                    pre.next = cur.next;
                }else{
                    pre = pre.next;
                }

                cur = cur.next;
            }
            return dummy.next;
    }
}