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){
            return null;
        }
        HashMap<Integer,ListNode> dq=new LinkedHashMap<>();

        ListNode tmp=head;
        int rm=0;
        //HashSet<Integer> hm=new HashSet<>();
        while(tmp!=null){
            if(dq.containsKey(tmp.val)){
                dq.remove(tmp.val);
                rm=tmp.val;
                //System.out.println(dq);
            }
            else if(tmp.val!=rm){
                dq.put(tmp.val,tmp);
            }
            tmp=tmp.next;
        }
        ListNode dummpy=new ListNode(1);
        ListNode res=dummpy;
         System.out.println(dq);
        for(Integer i:dq.keySet()){
             //System.out.println(i);
            dummpy.next=dq.get(i);
            dummpy=dummpy.next;
        }
        dummpy.next=null;
        return res.next;
    }

    
}