😔😔😔
import java.util.*; public class Solution { public ListNode deleteDuplicates (ListNode head) { if(head==null||head.next==null) return head; ListNode newHead = new ListNode(0); ListNode pre = newHead; HashMap<Integer,Integer> hm = new LinkedHashMap<>(); while(head!=null) { if(hm.containsKey(head.val)) hm.put(head.val,hm.get(head.val)+1); else hm.put(head.val,1); head = head.next; } for(Integer keys : hm.keySet()){ if(hm.get(keys)==1){ pre.next = new ListNode(keys); pre = pre.next; } } pre = null; return newHead.next; } }