problem.md

Problem 173: Binary Search Tree Iterator

Difficulty: Medium

Problem

Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST.

Calling next() will return the next smallest number in the BST.

Note: next() and hasNext() should run in average O(1) time and uses O(h) memory, where h is the height of the tree.

Example

Input: [5,2,7,1,3,6,9]
Output: [1,2,3,5,6,7,9]