Coding & Algorithms Interview Questions
Practice 2,960 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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Solve String Addition and Expression Evaluation
The interview included two coding problems: 1. Add numbers from character arrays - You are given two non-empty character arrays, where each array r...
Solve small string and API tasks
You are given three small programming tasks (typical “easy” difficulty). Implement each as a function. Task 1: Validate parentheses Given a string s c...
Find degrees of connection in a LinkedIn graph
You are given an undirected graph representing professional connections: - n people labeled 0..n-1 - a list of undirected edges connections, where (a,...
Solve Three Array Coding Problems
An online assessment contains the following three independent coding problems. For each problem, write a function that returns the requested value. Us...
Compute Inherited Role Privileges
You are given n roles. The array initialPrivileges has length n, where initialPrivileges[i] is the list of privileges directly assigned to role i. You...
Find minimum subarray length with k distinct integers
Given an integer array arr and an integer k, find the minimum length of a contiguous subarray that contains exactly k distinct integer values. Return ...
Design and implement an LRU cache
Problem Design and implement an LRU (Least Recently Used) Cache that supports the following operations in O(1) average time: - get(key) → returns the ...
Count queen attacks on points with blockers
You are given positions on an (unbounded) 2D integer grid. - queens: coordinates of queens - points: query coordinates A queen attacks along 8 directi...
Validate whether a binary string is good
You are given a binary string s consisting only of characters '0' and '1'. Define a good string recursively by the grammar: - '0' is a good string. - ...
Compute city skyline outline
You are given a list of rectangular buildings in a 2D city skyline. Each building is represented by three integers [L, R, H]: - L: the x-coordinate of...
Compute cart total with best promotion
Assume you are implementing a checkout price calculator for an online shopping cart. You are given: - A list of items in the cart. Each item has: - ...
Paginate forward and backward through results
You are asked to extend a basic pagination system to support forward and backward navigation, similar to a cursor-based API. You are given: - A zero-i...
Design document editor with undo/redo and batching
Design a document-editing layer that supports applying edits and undo. Implement an API with apply(Operation op), undo(), and getText(). Then add tran...
Evaluate query ratios from equations
You are given equations of the form A / B = value where A and B are variable names (strings) and value is a positive real number. You also receive que...
Solve Morse and Network Access Tasks
Solve the following two independent coding problems. Problem 1: Convert Between Text and Morse Code You are given the standard Morse-code mapping for ...
Design a rolling hit counter API
Rolling hit counter (time/space optimized) Design a data structure that records events (“hits”) and can return how many hits happened in the most rece...
Design a logger that returns top-K messages
Problem Design an in-memory logging component that supports recording log events and querying the top K most frequent messages. Each log event has: - ...
Implement four string-processing functions
You are given four independent string/list problems. Implement each as a separate function. 1) Filter strings by shared characters Input: - words: a l...
Implement array parity and tree level views
Implement the following coding tasks. 1. Check whether all values occur an even number of times - Input: an integer array nums. - Output: return...
Implement Autoregressive Decoding Strategies
You are given a simplified autoregressive language model. The model receives a 1D sequence of token IDs and returns logits for the next token. The voc...