TikTok interview questions

Find Median from Data Stream

Maintain a data structure that supports adding integers from a stream and returning the current median efficiently for many interleaved addNum and findMedian calls. The…

Companies: TikTok, Adobe, Amazon, D. E. Shaw +4

Data Stream · Design · Heap (Priority Queue) · Sorting

Find the longest palindromic substring in a string

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Gas Station

Given two arrays gas and cost around a circular route, find the unique starting station index from which you can travel clockwise once without your…

Companies: TikTok, Adobe, Bloomberg, Expedia +2

Array · Greedy

General background questions personal infos

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Given two strings s and t, return the minimum window substring of s that contains every character of t including duplicates, or an empty string if no such window exists. Walk through the sliding-window approach using two pointers and a character-frequency hashmap, analyze the O(|s| + |t|) time complexity, and discuss how to adapt it when t contains characters not present in s or when s arrives as a stream that cannot be fully buffered.

Given two strings s and t, return the minimum window substring of s that contains every character of t including duplicates, or an empty string…

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How do you choose a classification threshold?

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How would you manage precision/recall for fraud detection?

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Implement a DFS for a matrix to find a certain value

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Implement an LRU cache with O(1) operations

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Implement AUC-ROC, softmax, and logistic regression

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just coding questions, no behavior

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Longest Mountain in Array

Find the length of the longest contiguous "mountain" subarray — a strictly increasing sequence immediately followed by a strictly decreasing sequence with length ≥ 3…

Companies: TikTok, Oracle

Array · Dynamic Programming · Enumeration · Two Pointers

Longest Substring with At Most K Distinct Characters

Given a string and an integer K, find the length of the longest substring that contains at most K distinct characters. This is typically solved…

Companies: TikTok, LinkedIn

Hash Table · Sliding Window · String

LRU Cache

Implement an LRUCache that supports O(1) average-time get(key) returning the value or -1 and put(key, value) which inserts or updates a key and, if capacity…

Companies: TikTok, Adobe, Amazon, Anthropic +29

Data Structure Design · Design · Doubly-Linked List · Hash Table

LRU Cache Question on Leetcode

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Making A Large Island

Given an n×n binary grid where you can flip at most one 0 to 1, compute the largest possible 4-directional island size after the flip…

Companies: TikTok, DoorDash, Meta, Uber

Array · Breadth-First Search · Depth-First Search · Matrix

Meeting Rooms II

Given a list of meeting time intervals, determine the minimum number of conference rooms required so that no meetings overlap. The core challenge is computing…

Companies: TikTok, Amazon, Apple, Google +9

Array · Greedy · Heap (Priority Queue) · Prefix Sum

Merge Intervals

Given a list of intervals, merge all overlapping (including touching endpoints) intervals and return the minimal set of non-overlapping intervals that cover them. Key pattern…

Companies: TikTok, Amazon, Antithesis, Apple +16

Array · Quicksort · Sorting

Partition Array for Maximum Sum

Partition the array into contiguous subarrays of length at most k, replace every value in a subarray with that subarray's maximum, and maximize the resulting…

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Array · Dynamic Programming

Path Sum III

Count how many downward paths (parent→child, can start and end at any nodes) in a binary tree sum to a given target. The challenge is…

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Binary Tree · Depth-First Search · Tree

Personalize Ad Delivery Using Machine Learning Techniques

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Possible Bipartition

Given n people and pairwise dislikes, determine whether the corresponding undirected graph is bipartite — i.e., whether you can 2-color all vertices (split into two…

Companies: TikTok, LinkedIn, Uber

Bipartite Graph · Breadth-First Search · Depth-First Search · Graph Coloring