删除链表中重复的结点

在一个排序的链表中，存在重复的结点，请删除该链表中重复的结点，重复的结点不保留，返回链表头指针。 例如，链表1->2->3->3->4->4->5 处理后为 1->2->5

/*
 public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}
*/
public class Solution {
    public ListNode deleteDuplication(ListNode pHead){
        
        ListNode preHead = new ListNode(-1);
        preHead.next = pHead;
        
        ListNode cur = pHead;
        ListNode pre = preHead;
        
        while (cur != null && cur.next != null) {
            if (cur.val == cur.next.val) {
                int val = cur.val;
                while (cur != null && cur.val == val) {
                    cur = cur.next;
                }
                pre.next = cur;
            }
            else {
                pre = cur;
                cur = cur.next;
            }
        }
        return preHead.next;
    }
}