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)
    {
        if(pHead == null || pHead.next == null){
            return pHead;
        }
        ListNode node = new ListNode(0);
        node.next = pHead;
        ListNode preNode = node;
        ListNode cur = pHead;
        while(cur != null){
            while(cur != null && cur.next != null && cur.val == cur.next.val){
                cur = cur.next;
            }
            if(preNode.next != cur){
                preNode.next = cur.next;
                cur = cur.next;
            }else{
                preNode = cur;
                cur = cur.next;
            }
        }
        return node.next;
    }
    
}