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Problem 129

Binary Search Tree Iterator

MediumBST

Implement a BST iterator with next() (next inorder value) and hasNext(). Tests call bstIterator(ops, args) on the class. Seed with the tree array passed to the constructor.

Examples

Example 1

Input: BSTIterator([7,3,15,null,null,9,20]) then next, next, hasNext…

Output: [3,7,true,9,true,15,true,20,false]

Constraints

The number of nodes is in [1, 10⁵]

Target ComplexityNot required

O(n) Time · O(n) Space

Companies (5)

AmazonGoogleMetaMicrosoftApple

Node 22.08.0

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Test casesRun to compare output

InputBSTIterator([7,3,15,null,null,9,20]) then next, next, hasNext…

Expected[3,7,true,9,true,15,true,20,false]

Output—