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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Merge overlapping intervals
Given a list of half-open numeric intervals [start, end), merge all overlapping or contiguous intervals and return a list of non-overlapping intervals...
Implement Due Broadcast Sender
You are building a notification system. You are given: - A mapping from company_id to a list of subscriber IDs. - A list of broadcast logs. Each log c...
Find shortest subarray to restore order
Given an integer array, find the shortest contiguous segment which, if sorted in ascending order, makes the entire array non-decreasing. Return the le...
Implement transaction network queries
Problem You are building a small in-memory library to track pairwise customer transactions and answer connectivity questions about who has transacted ...
Compute Fibonacci Numbers
Write a function that returns the nth Fibonacci number. Definitions and requirements: - Use zero-based indexing: fib(0) = 0, fib(1) = 1. - For n >= 2,...
Compute shortest path in cyclic graph
Problem: Shortest Path in a Graph With Cycles You are given a directed weighted graph that may contain cycles. - There are n nodes labeled 0..n-1. - Y...
Find earliest time all riders become connected
You are given a time-ordered log of events involving Uber riders. Each event has a timestamp and two rider names. Event types: 1. t X shared-ride-with...
Solve three algorithm tasks
Solve the following algorithm tasks and explain your approach, time complexity, and space complexity for each: 1) Fully justify text: Given an array o...
Find k most frequent in linear time
Given an integer array nums and an integer k (1 ≤ k ≤ number of distinct values in nums), return any k values that appear most frequently. Implement a...
Count permutations with exactly n inversions
You are given two integers m and n. Consider all permutations of the array [1, 2, ..., m] (each number from 1 to m appears exactly once). A permutatio...
Minimize time using elevator then climb stairs
Problem You need to go up n floors (from floor 0 to floor n). You may: 1. Take the elevator first (at most once, only at the start) for k floors, wher...
Implement Snapshot Iterator Without Order Guarantees
Design and implement a mutable collection that supports snapshot iteration. The collection stores unique values and supports the following operations:...
Solve Cache, Window, and Heap Problems
You may be asked to solve multiple algorithmic problems in coding rounds: 1. Frequency-based cache: Implement a cache with get(key) and put(key, value...
Check whether an integer is a power of two
Given a signed 32-bit integer n, return true if n is an exact power of 2, otherwise return false. A power of 2 is a number of the form 2^k where k >= ...
Implement String Encryption and Decryption
Implement an encryption service for lowercase words. You are given: - keys: a list of distinct lowercase characters. - codes: a list of strings where ...
Aggregate expenses by person, trip, and category
Problem You are given a list of expense records. Each record has: - employee_id (string) - trip_id (string) - category (string, e.g., MEAL, HOTEL, TRA...
Compute distinct sums from limited coins
You are given two integer arrays, denom[0..n-1] and count[0..n-1], where denom[i] > 0 is a coin denomination and count[i] >= 0 is the number of availa...
Compute maximum beauty of a string
Given a string s, define the beauty of each letter a–z as a distinct integer between 1 and 26, case-insensitive. The beauty of a string is the sum ove...
Implement Terminal Tabs and Split Panels
Implement a data structure that models a terminal application with multiple tabs and split panels. Requirements: - A Terminal can create and store mul...
Design a CreditTracker with expirations
Design a CreditTracker class with three methods: ( 1) add_credit(start_time, end_time, credit), ( 2) subtract_credit(time, credit), and ( 3) check_cre...