CodingMediumcod-g053

Subject Binary search treeLevel Mid–Senior~20 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

Given a binary search tree as a level-order array `arr` (null for missing) and a 1-indexed integer `k`, return the value of the k-th smallest element. The tree is a valid BST with distinct values and `1 <= k <= node count`. `1 <= node count <= 100000`.

Implement

kth_smallest_bst(arr: list[int], k: int) → int

Examples

in[[3,1,4,null,2],1]out1

What a strong answer looks like

State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.

Learn the concepts

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.