Question
Given a binary tree encoded as a level-order array (None marks a missing child), return the number of nodes in the largest subtree that is itself a valid binary search tree (strict ordering: left subtree values < node < right subtree values). Solve it bottom-up in a single post-order pass: each node returns whether its subtree is a BST, its size, and its min/max so the parent can decide in O(1). Return the size of the largest such subtree.
largest_bst_subtree(level: list) → int[[10,5,15,1,8,null,7]]out3State 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.
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.