# Time: O(N)
# Space: O(N)

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
from collections import deque

class BSTIterator:
    items = None

    def __init__(self, root: Optional[TreeNode]):
        def inorder(node):
            return inorder(node.left) + [node.val] + inorder(node.right) if node else []
        
        # In-order traversal of a BST gives us values in
        # sorted order
        self.items = deque(inorder(root))

    def next(self) -> int:
        return self.items.popleft()

    def hasNext(self) -> bool:
        return len(self.items) > 0


# Your BSTIterator object will be instantiated and called as such:
# obj = BSTIterator(root)
# param_1 = obj.next()
# param_2 = obj.hasNext()