Frontier AI Technical Interview Question Bank

Topic tags
Python
Data structures
Storage & state
Data / SQL

Reported interview periodJan 2026–Jul 2026

Snapshot Iterator over a Mutable Set

Implement an insertion-ordered mutable set whose iterators observe a stable snapshot even as the live set changes.

Practice focusRequirements - Iteration follows current insertion order at iterator creation time. - Adding an already-present value changes nothing. - Removing and later re-adding a value places it at the end of the live order. - contains reflects current state, while an existing iterator continues to return exactly its snapshot. - next raises StopIteration after exhaustion. - Removing an absent value is a no-op. has next never advances an iterator, including repeated checks after exhaustion. Independent iterators have independent cursors.…

Free practice

Topic tags
Python
Data structures

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Jul 2026

Paths in an Implicit Fibonacci Tree

Define a Fibonacci tree of order k as a root whose left subtree has order k-1 and whose right subtree has order k-2. Nodes are labeled by their one-based preorder position. Compute paths without materializing t…

Practice focusRequirements - Use tree size(k) = F(k+2) - 1 , with F(0)=0 and F(1)=1 . - fib path returns node labels from start to end , inclusive. - fib directions returns "Up" steps to the lowest common ancestor, then "Left" or "Right" steps downward. - Validate that labels lie within the requested tree. - Order zero is an empty tree, order one is a single root, and subtrees of order zero or below are empty. Public orders must be non-negative non-boolean integers; labels must be non-boolean integers in 1..tree size(order) .…

New public brief

Topic tags
Python
Data structures
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Sep 2026

Minimize Encryption Work in a File Tree

A file hierarchy contains directories and files. Some files are already encrypted. You may encrypt an individual file or issue one recursive encryption request for an entire directory. Choose operations with mi…

Practice focusRequirements and cost model - Encrypting one file costs t req + t file . - Encrypting a directory costs t req + N t file , where N is every file in its subtree, including already-encrypted files. - A subtree with no unencrypted files costs 0 . - At a directory, you may batch the whole subtree or solve its children independently. count files returns (encrypted count, unencrypted count) . The input is a finite tree of FileNode and DirectoryNode objects, with boolean encryption flags, no cycles or shared nodes, and non-negative integer costs.…

Public brief

Topic tags
Python
Data structures

Coding exerciseCoding

Written response35 minutes

Reported interview periodN/A

Grade book

An in-memory grade book with a ranking that does not treat a missing score as zero.

Practice focusState, Ranking, Edge cases through a written response exercise.

Public brief

Topic tags
Python
Algorithms
Data structures

Coding exerciseCoding

Written response40 minutes

Reported interview periodN/A

Launch order

Return one valid order of steps, or report a cycle.

Practice focusOrdering, Cycles through a written response exercise.

Frontier AI technical interview question bank.

Frontier AI technical interview question bank.

Snapshot Iterator over a Mutable Set

Paths in an Implicit Fibonacci Tree

Minimize Encryption Work in a File Tree

Grade book

Launch order

Snapshot Iterator over a Mutable Set

Paths in an Implicit Fibonacci Tree

Minimize Encryption Work in a File Tree

Grade book

Launch order