82. Remove Duplicates from Sorted List II（删除有序链表中的重复元素）

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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.

class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode fakehead= new ListNode(0);
        fakehead.next = head;
        ListNode pre = fakehead;
        ListNode cur =head;
        while(cur!=null){
            while(cur.next!=null&&cur.val == cur.next.val)
                cur = cur.next;
            if(pre.next !=cur)
                pre.next = cur.next;
            else 
                pre = pre.next;
            cur = cur.next;
        }
        return fakehead.next;
    }
}