173. Binary Search Tree Iterator

Python

class BSTIterator:
    def __init__(self, root: Optional[TreeNode]):
        tree = []

        def inorder(node):
            if not node:
                return
            inorder(node.left)
            tree.append(node.val)
            inorder(node.right)

        inorder(root)
        
        self.root = root
        self.tree = tree
        self.cur = 0

    def next(self) -> int:
        result = self.tree[self.cur]
        self.cur += 1
        return result

    def hasNext(self) -> bool:
        return self.cur < len(self.tree)
Python​

Python
