Coding (Algo)

Binary search tree validation: propagate strict value bounds through the entire tree

Binary search tree validation: Given a binary tree in zero-based heap-indexed level order, return whether it is a strict binary search tree. Null entries represent missing nodes and duplicate values are invalid.

Input: A JSON object { "tree": (number|null)[] }.

Output: A JSON boolean.

Constraints:

0 <= tree.length <= 100000
Every non-null value is a safe integer
The BST rule applies against all ancestors, not only the parent

Read one JSON value from stdin and print exactly one JSON-serialized answer to stdout with no extra text.

Difficulty: MEDIUM. Variant: 20. Expect follow-up questions about complexity, edge cases, and alternative approaches.

Practice context

This coding (algo) exercise trains prompt interpretation, explicit assumptions, a concrete response, and a concise explanation of the decisions made. It is marked medium difficulty.

The signed-in workspace provide

What this task practices

This coding (algo) exercise trains the same sequence expected in an interview: understand the prompt, make assumptions explicit, produce a concrete answer, and explain the decisions behind it. The task is marked medium difficulty. The private workspace adds the tools required by this round, such as recording, code execution, diagrams, evidence panels, or structured notes. It also preserves the attempt so later feedback can be compared with previous work. Evaluation is based on task-specific criteria and the candidate seniority selected in the preparation path. Public pages never expose the reference solution, hidden tests, evaluator instructions, or another candidate’s work.