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."
Implement DelayQueue with Idempotent Task Execution
Scenario Message broker offers DelayQueue where tasks execute at future timestamps, ensuring idempotency on duplicate IDs. Question Implement a delay ...
Find Path Between Fibonacci Tree Nodes
You are given a special family of binary trees called Fibonacci trees. Define the tree T(k) recursively: - T(1) is a single node. - T(2) is a single n...
Maximize one stock trade profit
You're given an array prices of length n where prices[i] is the stock price on day i. You may complete at most one transaction (buy once, then sell la...
Implement prioritized refund allocation engine
Implement a refund allocation function that takes: (a) a list of payments, each with a unique paymentId, method ∈ {CREDIT, CREDIT_CARD, PAYPAL}, ISO-8...
Find minimum time for irrecoverable password
A password is a string s of length n. A virus attacks positions in a 1-indexed order given by a permutation attackOrder[1..n]. At second t (1 <= t <= ...
Solve six algorithmic problems
Answer the following independent algorithmic prompts. For each, explain your approach, justify data structures, analyze time/space complexity, and pro...
Clone list with random pointers
Question You are given the head of a singly linked list where each node has two pointers: next and random. The random pointer may be null or point to ...
Solve grid path and top‑k frequency
Part A — Grid Reachability with Obstacles: Given an m×n matrix of 0s and 1s where 0 indicates a passable cell and 1 indicates a blocked cell, starting...
Solve minimum rate and subset sum
1) Minimum rate to finish vaults within a deadline: You are given an array vaults of positive integers representing the amount in each vault along a r...
Solve grid compromise spread with BFS
You are given an m×n grid representing a data center: 0 = empty rack, 1 = secure server, 2 = compromised server. Each minute, any secure server that i...
Implement file deduplication at scale
Implement a command-line tool to find duplicate files in a directory tree. Use OS/pathlib primitives to recursively enumerate files. Apply prefilters ...
Optimize ribbon piece length by binary search
Given an array lengths of positive integers and an integer k, you may cut each element into pieces of integer length L > 0. Find the maximum L such th...
Detect cycles in lists and graphs
Given a singly linked list, determine whether it contains a cycle. Implement an O( 1)-space algorithm and explain the intuition and correctness. Follo...
Find shortest path using BFS
Given an m×n grid grid where grid[r][c] = 0 represents an empty cell and 1 represents a wall, a start cell (sr, sc), and a target cell (tr, tc), you m...
Design a music player with favorites cap
Implement an in-memory music player that supports: addSong(id, metadata), removeSong(id), play(id), pause(), next(), prev(), getNowPlaying(), queueSon...
Compute discounted prices in a queue
Given an integer array prices where prices[i] is the price of the i-th item in a checkout line, apply the following rule: for each i, find the first j...
Solve path normalization and nested iterator
1) Normalize Unix-style absolute paths: Given a string representing an absolute Unix file path, return its canonical form. Rules: '.' refers to the cu...
Design a parser for a hypothetical language
You are given a set of syntax rules for a hypothetical programming language written in BNF/EBNF. Design data structures and algorithms that: ( 1) pars...
Count connected delivery zones
Given an m x n grid representing a service area, each cell is either 'Z' (deliverable zone) or '#' (blocked). Two 'Z' cells belong to the same zone if...
Implement image carousel with comments and upvotes
Implement an image carousel that supports: 1) cycling forward/backward and autoplay with a configurable interval; 2) a per-image comment thread with c...