README_EN.md

173. Binary Search Tree Iterator

Description

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.

 

Example:

BSTIterator iterator = new BSTIterator(root);

iterator.next();    // return 3

iterator.next();    // return 7

iterator.hasNext(); // return true

iterator.next();    // return 9

iterator.hasNext(); // return true

iterator.next();    // return 15

iterator.hasNext(); // return true

iterator.next();    // return 20

iterator.hasNext(); // return false

 

Note:

<li><code>next()</code> and <code>hasNext()</code> should run in average O(1) time and uses O(<i>h</i>) memory, where <i>h</i> is the height of the tree.</li>

<li>You may assume that&nbsp;<code>next()</code>&nbsp;call&nbsp;will always be valid, that is, there will be at least a next smallest number in the BST when <code>next()</code> is called.</li>

Solutions

Python3

Java

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