from typing import Optional
from utils import ListNode, list_to_linklist, deleteNode, linkList_to_arr

def deleteDuplicates(head: Optional[ListNode]) -> Optional[ListNode]:
    if not head:
        return head
    # p = head
    # while p.next:
    #     if p.val == p.next.val:
    #         p.next = p.next.next
    #     else:
    #         p = p.next
    #
    # return head
    # p = head
    # while p and p.next:
    #     q: ListNode = p.next
    #     # 寻找跟p不同val的节点
    #     # 找到的时候q指向了它
    #     while q and q.val == p.val:
    #         q = q.next
    #     p.next = q
    #     p = q
    # return head

    p = head
    q = head.next
    while q:
        if q.val == p.val:
            p.next = q.next
            q = q.next
        else:
            p = q
            q = q.next

    return head

res = deleteDuplicates(list_to_linklist([1]))
print(linkList_to_arr(res))