Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.
For example,
Given

1->2->3->3->4->4->5

, return

1->2->5

.
Given

1->1->1->2->3

, return

2->3

.

public class Solution {
public ListNode deleteDuplicates(ListNode head) {
if(head==null || head.next==null) return head;
ListNode safe = new ListNode(-1);
safe.next = head;
ListNode pre = safe;
ListNode cur = head;
ListNode post = head.next;
while(post!=null){
if(post.val==cur.val){
while(post!=null && post.val==cur.val){
cur = post;
post = post.next;
}
cur = post;
if(post!=null)
post = post.next;
continue;
}
pre.next = cur;
pre = cur;
cur = post;
if(post!=null)
post = post.next;
}
pre.next = cur;
return safe.next;
}
}

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