ByteDance and TikTok interview questions for engineers

Topic tags
Python
Algorithms
Concurrency

Reported interview periodNot available

Clockwise Spiral Matrix

Return all values of an m × n matrix in clockwise spiral order, beginning at the top-left corner.

Practice focusUse O(1) auxiliary space excluding the returned list, and do not mutate the matrix. Handle empty, single-row, single-column, square, and rectangular matrices. Staged follow-ups 1. Generate an n × n matrix filled from 1 through n² in spiral order. 2. Expose a lazy iterator rather than building the result. 3. Traverse counterclockwise or from an arbitrary corner without duplicating the entire algorithm.

Free practice

Topic tags
Python
Algorithms

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Longest Substring Without Repeated Characters

Given a string, return the length of its longest contiguous substring containing no repeated character.

Practice focusThe empty string returns 0 . Treat characters as the language runtime's Unicode characters. Target O(n) time and O(k) space, where k is the number of distinct characters in the active input. Staged follow-ups 1. Return the substring or its half-open index range, not just its length. 2. Permit each character to appear at most m times. 3. Process a stream in chunks without retaining the entire prefix.

Free practice

Topic tags
Python
Algorithms

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Merge Closed Intervals

Given a list of closed intervals [start, end], merge every overlapping pair and return the resulting non-overlapping intervals sorted by start position.

Practice focusAssume start <= end . Because intervals are closed, [1, 4] and [4, 6] overlap and become [1, 6] . The input may be unsorted and may contain duplicates. Staged follow-ups 1. Preserve associated metadata while merging. 2. Insert one interval into an already sorted, disjoint sequence. 3. Process intervals that arrive as a stream and discuss when output can be finalized.

Free practice

Topic tags
Python
Algorithms

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Minimum Interval Removals

Given intervals [start, end], remove as few as possible so that the remaining intervals do not overlap. Intervals that only touch at an endpoint are compatible.

Practice focusAssume every interval satisfies start <= end . The input may be unsorted and may contain duplicates. Target O(n log n) time. Staged follow-ups 1. Return the retained or removed interval indices. 2. Assign positive weights and maximize retained weight rather than retained count. 3. Handle online arrivals and explain which guarantees can no longer be optimal.

Free practice

Topic tags
Python
Algorithms

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Number of Islands

Given a rectangular grid of characters, where '1' is land and '0' is water, return the number of edge-connected land components. Diagonal cells are not connected.

Practice focusThe grid may be empty. You may either mutate the grid or maintain separate visited state, but state your choice. Target O(rows columns) time. Staged follow-ups 1. Return the area of the largest island. 2. Count islands as land cells are added incrementally. 3. Process a grid too large to hold fully in memory, one row at a time.

Free practice

Topic tags
Python
Data structures

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Reverse a Singly Linked List

Given the head of a singly linked list, reverse its links in place and return the new head.

Practice focusDo not allocate a second list. An empty list and a one-node list should be returned unchanged. The iterative solution should use O(1) auxiliary space. Staged follow-ups 1. Provide a recursive implementation and compare its space usage. 2. Reverse only the nodes between positions left and right . 3. Reverse nodes in fixed-size groups while leaving a final short group unchanged.

Free practice

Topic tags
Python

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Valid Bracket Sequence

Given a string containing only (, ), [, ], {, and }, determine whether every opener is closed by the matching type in the correct order.

Practice focusThe empty string is valid. A closing bracket with no pending opener is invalid, as is any opener left at the end. Target O(n) time and O(n) worst-case space. Staged follow-ups 1. Ignore brackets inside quoted strings while respecting escape characters. 2. Report the location and expected token for the first mismatch. 3. Validate a stream incrementally across chunk boundaries.

New public brief

Topic tags
Python

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Best Time to Buy and Sell Stock

Given daily prices, compute the maximum profit obtainable by buying once and selling once later. You may choose not to trade, in which case the profit is 0.

Practice focusPrices are non-negative integers. An empty or one-day input returns 0 . Solve the problem in O(n) time and O(1) auxiliary space. Staged follow-ups 1. Allow any number of non-overlapping transactions while holding at most one share. 2. Add a fixed transaction fee or a one-day cooldown after selling. 3. Return the chosen buy and sell days with deterministic tie-breaking.

New public brief

Topic tags
Python
Algorithms

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Binary Search

Given a strictly increasing array of integers and a target, return the target's index or -1 when it is absent.

Practice focusThe solution must run in O(log n) time and use O(1) auxiliary space. An empty array returns -1 . Staged follow-ups 1. Return the first position where the target could be inserted while preserving order. 2. Support duplicate values by returning the first matching index. 3. Search a conceptually unbounded sorted data source through a bounded-access interface.

New public brief

Topic tags
Python

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Count Values with an Even Number of Digits

Given a list of positive integers, return how many contain an even number of decimal digits.

Practice focusFor example, [12, 345, 2, 6, 7896] returns 2 . Assume every value is positive and fits in a signed 32-bit integer. Target O(n) time. Staged follow-ups 1. Extend the definition to include zero and negative integers without counting a sign. 2. Avoid converting numbers to strings. 3. Count digits in an arbitrary base supplied at runtime.

New public brief

Topic tags
Python
Storage & state

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Course Schedule

There are num_courses courses labeled 0 through num_courses - 1. Each prerequisite pair (course, prerequisite) states that the prerequisite must be completed first.

Practice focusImplement: Return whether it is possible to complete every course. Courses with no edges are valid, and duplicate prerequisite pairs should not change the answer. Aim for O(V + E) time. Staged follow-ups 1. Return one valid course order, or an empty list when none exists. 2. Return an explicit cycle to explain why the schedule is impossible. 3. Process prerequisite additions incrementally and reject an addition that creates a cycle.

New public brief

Topic tags
Python

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Maximum Non-Adjacent Sum

Each value in amounts is the reward available at one location. You may select any subset, but cannot select two adjacent locations. Return the largest total reward.

Practice focusAssume rewards are non-negative. The empty input returns 0 . Produce an O(n) -time solution and then reduce its auxiliary space to O(1) . Staged follow-ups 1. Return the selected indices, with deterministic tie-breaking. 2. Arrange the locations in a circle, so the first and last are also adjacent. 3. Generalize to a tree where directly connected nodes cannot both be selected.

Public brief

Topic tags
Python
Algorithms

ByteDanceCoding

Talk-through codingNo local grader

Reported interview periodNot available

Palindrome Integer

Determine whether a signed 32-bit integer reads identically from left to right and right to left in decimal notation.

Practice focusNegative numbers are not palindromes because of the sign. A positive number ending in zero is not a palindrome unless the value itself is zero. Staged follow-ups 1. Solve without converting the number to a string. 2. Reverse only half the digits to avoid overflow and unnecessary work. 3. Generalize the check to an arbitrary base from 2 through 36.

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

Coding exerciseCoding

Written 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

Written 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

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.

Public brief

Topic tags
Storage & state
Reliability

System designSystem design

Written response45 minutes

Reported interview periodN/A

Shared scratch pad

Two people edit one note and need to see who wrote the last line.

Practice focusConflict, Failure through a written response exercise.

Public brief

Topic tags
Communication

Hiring manager practiceHiring manager

Written 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

Written 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

Written 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

Written 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.