dsa · medium

Binary Search Tree Iterator

GreyOrangeTreeStackDesign

BSTIterator(root) then next / hasNext over **inorder**. Tree encoding [val,left,right].

Fill in the BSTIterator class. The starter already walks ops / args and calls your methods — leave the driver at the bottom as-is. Constructors contribute null; booleans print as true / false.

**Example**

`` BSTIterator([7,[3,null,null],[15,[9,null,null],[20,null,null]]]) → null next() → 3 next() → 7 hasNext() → true next() → 9 hasNext() → true ``

Constraints

Number of nodes <= 100

Examples

Example 1

Input:
["BSTIterator","next","next","hasNext","next","hasNext"]
[[[7,[3,None,None],[15,[9,None,None],[20,None,None]]]],[],[],[],[],[]]

Expected:
[null,3,7,true,9,true]

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