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Question bank

Frontier AI technical interview question bank.

Practice coding, system design, behavioral, and project questions for frontier AI roles.

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Home
Question bank

Frontier AI technical interview question bank.

Practice coding, system design, behavioral, and project questions for frontier AI roles.

Company

FREE PRACTICE

Public demos, always pinned.

Start with either demo. They remain here when you filter or sort.

Free account: sign in to practice the marked Free questions.

Newest published questions; deterministic, never randomized.

Demo 1Number search with delayed feedback
Demo 2Design real-time device monitoring and control

Question bank filters

Reset filters

Question groups

Filter question bank by interview groupAll 48 Coding 40 System design 2 Behavioral 3 Hiring manager 1 Project deep dive 2

Topics

Filter question bank by topic tagsAll 48 Python 40 Algorithms 12 Data structures 10 Concurrency 2 Storage & state 3 Reliability 2 Data / SQL 1 Product design 1 Communication 6

Independent and not affiliated with the companies represented. Collected material does not predict future interview questions.

45 questions

Sort question bankSortFree first Newest Oldest AI ratio ↓AI ratio ↑

Question bank results

Every question has a public brief with the task, constraints, and follow-ups. Labels describe interactive practice access.

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Aug 2026

Shared ancestor of two nodes in a binary tree

A binary tree arrives in level-order form along with two node values. Identify the lowest node whose subtree contains both values.

Practice focusRequirements - Line one is the level-order values separated by commas; null marks a missing child and the line may be wrapped in [...] . - Line two holds the two target values separated by a comma. - Node values are unique, and both targets appear in the tree. - A node counts as its own descendant, so a parent and child query answers the parent. - Return the value of the lowest shared ancestor as a decimal string, not its position in the serialization. - When one candidate ancestor lies below another, report the deeper one.…

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Pick the longest letter-disjoint word group

Given a list of lowercase words, choose a group in which no letter repeats, either inside a single word or across words, and report the largest total number of letters such a group can contain.

Practice focusRequirements - Line 1 holds the number of words. Line 2 holds exactly that many space-separated lowercase words. - A word may join the group only if all of its own letters are different. - No letter may be shared by two chosen words, so each of the 26 letters appears at most once in the whole group. - Words may be skipped, and selecting no words is allowed. - Maximize the total character count across the chosen words. - Return that maximum as a decimal string, using "0" when no word qualifies.…

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Leftmost local maximum in a numeric sequence

Given a sequence whose adjacent values never tie, locate the first element that rises above every neighbor it has. Report that element's position.

Practice focusRequirements - The input is one line of space-separated integers with no count prefix, and it holds at least one value. - A position is a local maximum when its value is strictly greater than each neighbor that exists; the first and last positions have only one neighbor. - Return the zero-based index of the earliest such position as a decimal string. - A single-element sequence qualifies at index 0 . - Because neighbors never tie, at least one local maximum always exists and no equality rule is needed.…

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodMar 2026–Aug 2026

Count contiguous runs with a target sum

Given an integer array and a target, count the non-empty contiguous runs whose values add up to that target. Values may be zero or negative, so a qualifying run can begin and end anywhere.

Practice focusRequirements - The first line holds the element count and the target, separated by a space; the second line holds the values. - A variant layout puts only the count on the first line, the values on the second, and the target on the third; read the target from whichever position it occupies. - Count every start and end pair, including single elements and runs whose values are all zero. - The empty run never counts, and overlapping runs are counted separately. - Return the count as a decimal string with no other text.…

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Jul 2026

Column order of a binary tree

Rebuild a binary tree from its level-order serialization, then group the node values by column, moving left to right across columns. Inside one column the values should follow the order in which a breadth-first…

Practice focusRequirements - The first line is a level-order serialization separated by commas. A missing child is written as null , and the whole line may optionally be wrapped in square brackets. An empty line or [] means there is no tree. - Children attach in queue order: each non-null node consumes the next two slots as its left child and then its right child. - The root sits in column 0; a left edge shifts the column by -1 and a right edge by +1 . - Emit one inner list per occupied column, ordered from the smallest column offset to the largest.…

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJun 2026

Shortest distinguishing prefix per word

Given a list of distinct lowercase words, return for each word the shortest opening slice that no other word in the list also starts with, preserving input order.

Practice focusRequirements - The first input line is the word count n ; the next n lines each hold one lowercase word. - Emit one prefix per line in input order, joined by newlines, with no summary line and no trailing separator. - Each prefix must be a leading slice of its own word and must not be a leading slice of any other word in the list. - Prefer the shortest qualifying slice: extend the prefix only until the character that no other word shares at that depth. - A list holding a single word uses that word's first character.…

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–May 2026

Kth largest value with duplicates counted

Return the k-th value in descending order from an integer array, treating equal values as separate entries. The input arrives in one of two line layouts.

Practice focusRequirements - Layout A: line one is the element count, line two holds the integers, and line three is k . - Layout B: line one is nums=[3,2,1,5,6,4] and line two is k=2 , with no space before either equals sign. - k is one-based and always lies between 1 and the array length, so k = 1 asks for the maximum and k equal to the length asks for the minimum. - Return the selected value as a decimal string; it is a value, not a position.…

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Fewest inserts to balance brackets

Report how many bracket characters must be inserted anywhere in a parenthesis string to make every prefix and the whole line balanced.

Practice focusRequirements - The input is one line containing only ( and ) . - A string is balanced when every prefix has at least as many ( as ) , and the total counts are equal. - Insertions may be placed at any position. Removing, replacing, or reordering characters is not allowed. - Return the minimum number of inserted characters as a decimal string. - A line that is already balanced returns "0" . - run case(case: dict) forwards case["stdin"] to solve . - Do not append a trailing newline to the returned string; return the value exactly once.

Public brief

Topic tags
Python
Algorithms

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Tightest slice covering a character multiset

Find the shortest contiguous slice of a source string that contains every character of a required multiset with at least the required multiplicity, and return that slice.

Practice focusRequirements - Line 1 is the source string. Line 2 lists the required characters. - The chosen slice must be contiguous and must contain each required character at least as many times as it appears on line 2. - Compare slices by length. When several slices tie for the shortest length, return the one that begins earliest. - If no slice qualifies, return an empty string. - Matching is case-sensitive. - Return the slice itself, not its length and not its bounds. - run case(case: dict) forwards case["stdin"] to solve .…

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNot available

Maximum profit from repeated stock trades

You are given a price for each trading day and may complete as many round trips as you like, holding at most one share at a time. Report the largest total gain reachable across the whole window.

Practice focusRequirements - The input has two lines: a day count, then that many space-separated integer prices on the second line. The count matches the number of prices. - A round trip means buying one share on some day and selling it on a later day; positions cannot overlap and short selling is not allowed. - Return the total profit as a plain decimal string. A window with no profitable round trip, including a single day, yields 0 . - Prices are non-negative integers and the day count is at least one.…

Public brief

Topic tags
Python
Data structures

Coding exerciseCoding

Practice formatWritten 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

Coding exerciseCoding

Practice formatWritten response35 minutes

Reported interview periodN/A

Vial log

Return the vials that stayed inside a temperature range for their whole stay.

Practice focusScanning, Missing data through a written response exercise.

Public brief

Topic tags
Python
Algorithms

Coding exerciseCoding

Practice formatWritten response35 minutes

Reported interview periodN/A

Comment batches

Collapse consecutive comments on the same path into one batch.

Practice focusOrder, Grouping through a written response exercise.

Public brief

Topic tags
Python
Algorithms
Data structures

Coding exerciseCoding

Practice formatWritten 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.

Public brief

Topic tags
Communication

Behavioral practiceBehavioral

Practice formatWritten response20 minutes

Reported interview periodN/A

A thin check

A story about slowing a launch because a safety check was thin.

Practice focusJudgment, A specific story through a written response exercise.

Public brief

Topic tags
Communication

Behavioral practiceBehavioral

Practice formatWritten response20 minutes

Reported interview periodN/A

Customer text

A disagreement about training on customer text.

Practice focusDisagreement, Limits through a written response exercise.

Public brief

Topic tags
Communication

Behavioral practiceBehavioral

Practice formatWritten response10 minutes

Reported interview periodN/A

Why this work

Two minutes on why this lab's work fits a project you have done.

Practice focusA concrete project through a written response exercise.

Public brief

Topic tags
Communication

Hiring manager practiceHiring manager

Practice formatWritten response20 minutes

Reported interview periodN/A

Half the team

What you would cut if the team lost half its people.

Practice focusPriorities, A hard conversation through a written response exercise.

Public brief

Topic tags
Communication
Reliability

Project deep diveProject deep dive

Practice formatWritten response25 minutes

Reported interview periodN/A

After launch

Where a design failed after launch, what you measured, and what you changed.

Practice focusA shipped system, Measurement through a written response exercise.

Public brief

Topic tags
Python

Coding exerciseCoding

Practice formatWritten responseA weekend

Reported interview periodN/A

Notes table

Turn a folder of notes into a table of titles and word counts.

Practice focusA small program, What you left out through a written response exercise.

Public brief

Topic tags
Communication

Project deep diveProject deep dive

Practice formatWritten response20 minutes

Reported interview periodN/A

One result

Explain one result you trust, what would falsify it, and what was not shown.

Practice focusEvidence, Limits through a written response exercise.

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CONTENT BOUNDARY

Independent frontier AI interview practice. Includes adaptations of collected interview material and original exercises; not official company questions and not affiliated with the companies represented. Collected material does not predict future interview questions. Report a correction.

Loading the question catalog…

FREE PRACTICE

Public demos, always pinned.

Start with either demo. They remain here when you filter or sort.

Free account: sign in to practice the marked Free questions.

Newest published questions; deterministic, never randomized.

Demo 1Number search with delayed feedback
Demo 2Design real-time device monitoring and control

Question bank filters

Reset filters

Question groups

Filter question bank by interview groupAll 48 Coding 40 System design 2 Behavioral 3 Hiring manager 1 Project deep dive 2

Topics

Filter question bank by topic tagsAll 48 Python 40 Algorithms 12 Data structures 10 Concurrency 2 Storage & state 3 Reliability 2 Data / SQL 1 Product design 1 Communication 6

Independent and not affiliated with the companies represented. Collected material does not predict future interview questions.

45 questions

Sort question bankSortFree first Newest Oldest AI ratio ↓AI ratio ↑

Question bank results

Every question has a public brief with the task, constraints, and follow-ups. Labels describe interactive practice access.

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Aug 2026

Shared ancestor of two nodes in a binary tree

A binary tree arrives in level-order form along with two node values. Identify the lowest node whose subtree contains both values.

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Pick the longest letter-disjoint word group

Given a list of lowercase words, choose a group in which no letter repeats, either inside a single word or across words, and report the largest total number of letters such a group can contain.

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Leftmost local maximum in a numeric sequence

Given a sequence whose adjacent values never tie, locate the first element that rises above every neighbor it has. Report that element's position.

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodMar 2026–Aug 2026

Count contiguous runs with a target sum

Given an integer array and a target, count the non-empty contiguous runs whose values add up to that target. Values may be zero or negative, so a qualifying run can begin and end anywhere.

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Jul 2026

Column order of a binary tree

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJun 2026

Shortest distinguishing prefix per word

Given a list of distinct lowercase words, return for each word the shortest opening slice that no other word in the list also starts with, preserving input order.

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–May 2026

Kth largest value with duplicates counted

Return the k-th value in descending order from an integer array, treating equal values as separate entries. The input arrives in one of two line layouts.

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Fewest inserts to balance brackets

Report how many bracket characters must be inserted anywhere in a parenthesis string to make every prefix and the whole line balanced.

Public brief

Topic tags
Python
Algorithms

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Tightest slice covering a character multiset

Find the shortest contiguous slice of a source string that contains every character of a required multiset with at least the required multiplicity, and return that slice.

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNot available

Maximum profit from repeated stock trades

You are given a price for each trading day and may complete as many round trips as you like, holding at most one share at a time. Report the largest total gain reachable across the whole window.

Public brief

Topic tags
Python
Data structures

Coding exerciseCoding

Practice formatWritten 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

Coding exerciseCoding

Practice formatWritten response35 minutes

Reported interview periodN/A

Vial log

Return the vials that stayed inside a temperature range for their whole stay.

Practice focusScanning, Missing data through a written response exercise.

Public brief

Topic tags
Python
Algorithms

Coding exerciseCoding

Practice formatWritten response35 minutes

Reported interview periodN/A

Comment batches

Collapse consecutive comments on the same path into one batch.

Practice focusOrder, Grouping through a written response exercise.

Public brief

Topic tags
Python
Algorithms
Data structures

Coding exerciseCoding

Practice formatWritten 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.

Public brief

Topic tags
Communication

Behavioral practiceBehavioral

Practice formatWritten response20 minutes

Reported interview periodN/A

A thin check

A story about slowing a launch because a safety check was thin.

Practice focusJudgment, A specific story through a written response exercise.

Public brief

Topic tags
Communication

Behavioral practiceBehavioral

Practice formatWritten response20 minutes

Reported interview periodN/A

Customer text

A disagreement about training on customer text.

Practice focusDisagreement, Limits through a written response exercise.

Public brief

Topic tags
Communication

Behavioral practiceBehavioral

Practice formatWritten response10 minutes

Reported interview periodN/A

Why this work

Two minutes on why this lab's work fits a project you have done.

Practice focusA concrete project through a written response exercise.

Public brief

Topic tags
Communication

Hiring manager practiceHiring manager

Practice formatWritten response20 minutes

Reported interview periodN/A

Half the team

What you would cut if the team lost half its people.

Practice focusPriorities, A hard conversation through a written response exercise.

Public brief

Topic tags
Communication
Reliability

Project deep diveProject deep dive

Practice formatWritten response25 minutes

Reported interview periodN/A

After launch

Where a design failed after launch, what you measured, and what you changed.

Practice focusA shipped system, Measurement through a written response exercise.

Public brief

Topic tags
Python

Coding exerciseCoding

Practice formatWritten responseA weekend

Reported interview periodN/A

Notes table

Turn a folder of notes into a table of titles and word counts.

Practice focusA small program, What you left out through a written response exercise.

Public brief

Topic tags
Communication

Project deep diveProject deep dive

Practice formatWritten response20 minutes

Reported interview periodN/A

One result

Explain one result you trust, what would falsify it, and what was not shown.

Practice focusEvidence, Limits through a written response exercise.

Previous2 of 2Next

CONTENT BOUNDARY