题解 | #删除有序链表中重复的元素-II#

import java.util.*;

public class Solution {
    public ListNode deleteDuplicates (ListNode head) {
        ListNode node=head;
        HashMap<Integer,Integer> map=new HashMap<>();
        while(head!=null){
            if(map.containsKey(head.val)){
                map.put(head.val,map.get(head.val)+1);
            }else{
                map.put(head.val,1);
            }
            head=head.next;
        }
        ListNode list=new ListNode(-1);
        list.next=node;
        ListNode cur=list;
        while(node!=null){
            if(map.get(node.val)>1){
                list.next=list.next.next;
            }else{
                list=list.next;
            }
            node=node.next;
        }

        return cur.next;
    }
}