Coding & Algorithms Interview Questions
Practice 3,013 real Coding & Algorithms interview questions for 2026. Coding & Algorithms interview questions for top tech firms like Meta, Amazon, Google, Uber, and TikTok — real questions from actual interviews with detailed solutions — to power your interview preparation. This collection is sharply focused on algorithmic patterns (arrays, strings, sliding windows, trees/graphs, dynamic programming, greedy, two-pointers, and hashing), clean, review-ready code, and the explanation skills that distinguish hires. In 2026 expect familiar medium-to-hard problems plus newer twists: AI-enabled or multi-file coding rounds at some companies, more emphasis on explainability and edge-case reasoning, and occasional real-world performance constraints (streaming, concurrency, memory limits). Interviewers evaluate problem framing, algorithm choice, complexity trade-offs, test-case thinking, and communication under time pressure. Best prep mixes pattern-based practice, timed mock interviews, code-review style polishing, and rehearsed explanations of complexity and tradeoffs. Focus your last-mile prep on writing correct, readable code quickly and on explaining why your solution is robust and efficient for production scenarios.

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"Discovered PracHub 10 days before my interview. By day 5, I stopped being nervous. By interview day, I was actually excited to show what I knew."

"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
Convert stack samples to trace events
Question Implement convertToTrace(samples) that, given a chronologically ordered vector of stack samples (each sample contains a timestamp and a call-...
Find the k-th largest element in an array
Given an integer array nums and an integer k, return the k-th largest element in the array. Notes: - The k-th largest element is the element that woul...
Count connected land components in a grid
You are given a 2D grid of characters where: - '1' represents land - '0' represents water A group of land cells forms an island if they are connected ...
Merge two N-ary trees by key rules
You are given two N-ary trees A and B. Each node has: - key (string): unique among siblings (i.e., within a node’s children list, no two children shar...
Process Transactions and Compute Balances
You are given a list of financial transactions in CSV-like rows: ` account_name, timestamp, currency, amount ` - account_name is a string ID. - timest...
Determine Redeemable Promotion Offers
You are given predefined objects for promotion offers and user redemption events. A PromotionOffer has: - offer_id - start_time - end_time - max_redee...
Solve three algorithmic tasks in Python
You are given 120 minutes to implement three independent algorithmic tasks in Python. Each task specifies the required input/output behavior, the cons...
Implement a Worker Hours Register
Implement an in-memory WorkHoursRegister system for contract workers. The system tracks office entry and exit events, completed work time, promotions,...
Convert a PDF to a CDF
Given a continuous random variable X with probability density function f(x), write code or describe an algorithm to construct its cumulative distribut...
Solve SQL and Python coding tasks
You are given a small library system with the following relational schema and several Python data-processing tasks. Answer the SQL questions and imple...
Find median of two sorted arrays
You are given two sorted arrays of integers nums1 and nums2 in non-decreasing order. Let the lengths be m = nums1.length and n = nums2.length. Either ...
Find two numbers that sum to target
Given an integer array nums of length n and an integer target, return the indices (i, j) (0-based) of two distinct elements such that nums[i] + nums[j...
Build blog UI with API data and likes
You are asked to implement a small single-page web application in JavaScript (you may use any modern framework or plain JavaScript) to display and int...
Implement cluster status tracker
Implement a cluster status tracker. Design a class with methods: update(nodeId, status, timestamp) to record node status updates that may arrive out o...
Implement User Sessionization From Event Stream
You are building a backend data-processing component that consumes a stream of newline-delimited JSON events. Each event represents a user sending a m...
Solve top-K and string rotation match
1) Given an unsorted array of integers and an integer k, return the k largest elements in descending order. Implement at least two approaches (e.g., a...
Design order stream with state transitions
Implement an in-memory order stream service with operations: add(order), delete(order_id), pause(order_id), resume(order_id); follow-up: delete_all_by...
Implement Plus One
Given a non-empty array of digits representing a non-negative integer, where the most significant digit comes first and each element is in [0, 9], add...
Query Machines and Mark Them Offline
You are given access to a local HTTP server that simulates a production machine-management service. Write a program that queries the service, identifi...
Find a special person using knows(a,b)
Problem You are given n people labeled 0 to n-1 at a party. You can call an API: - knows(a, b) -> bool: returns true if person a knows person b, other...