# 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
class BSTIterator:

    def __init__(self, root: Optional[TreeNode]):
        self.node = root
        self.stack = []        

    def next(self) -> int:
        while self.node or self.stack:
            while self.node:
                self.stack.append(self.node)
                self.node = self.node.left 
            self.node = self.stack.pop()
            res = self.node.val
            self.node = self.node.right
            return res
        return None

    def hasNext(self) -> bool:
        return self.node or self.stack


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