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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Find minimum days to deliver all orders
You manage N delivery centers labeled 1..N and an array orderCityList where each element is the destination city of one order (city IDs are in 1..N). ...
Find grid cell minimizing sum distances
You are given an m x n 2D grid with k marked points. Movement is allowed in four directions (up, down, left, right) with unit cost per step. Find a gr...
Implement snake game and find org LCA
Part A — Snake Game Engine: Implement a grid-based snake game. The board has height H and width W (0-indexed, row-major). The snake starts at (0, 0) m...
Implement GPU credit ledger
You manage a GPU pool with per-tenant credits. Given a list/stream of events where each event adjusts a tenant’s credit balance by a signed integer (p...
Compute rightmost-smaller delay times
Given an integer array priorities, define delay[i] as the distance to the rightmost index j > i such that priorities[j] < priorities[i]; if no such in...
Solve three DSA problems: trie, window, intervals
1) Design and implement an autocomplete service. Support insert(word) to add a word and suggest(prefix) to return up to five existing words that start...
Design an elevator control system
Design the software for a multi-elevator control system in a high-rise building. Specify classes, scheduling algorithms for car assignments, handling ...
Solve vault rate and subset-sum
1) Robber vaults rate: You are given an array vaults of positive integers where vaults[i] is the amount in the i-th vault, and an integer h (hours). I...
Design a persistent key-value store
Design and implement an in-memory key-value store with a 'medium' layer that serializes the store to bytes for persistence. Provide four functions: se...
Compute square root with precision
Given a non-negative integer val and a non-negative integer precise, compute the square root of val without using any built-in square-root function. R...
Generate Instructions for a Blind Maze Robot
You are given a known 2D maze grid with m rows and n columns. Each cell is one of: - #: wall - .: empty cell - E: the exit, which appears exactly once...
Implement list cloning and k-frequency finder
You are given two separate coding tasks. --- Problem 1: Deep copy a linked list with extra pointers You are given the head of a singly linked list. Ea...
Find root IDs and paths
You are given a collection of string blocks, each represented as a JSON object with fields {"id": string, "parentId": string | null}. A block is a roo...
Implement a snapshotable set with iterators
Implement a SnapshotSet data structure with the following API: add(x), remove(x), contains(x), snapshot() -> sid, and iterate(sid) -> iterator over th...
Convert number words to integer
Given a line containing an English phrase representing a number in the range −999,999,999 to 999,999,999, convert it to its integer value. Supported w...
Implement a hierarchical key-value store
Implement an in-memory hierarchical key-value store where keys are UNIX-like paths joined by '/'. The root node is '/' with initial value '#'. Each no...
Maximize stock profit with constraints
Given an array prices of daily stock prices, you may make at most two complete transactions (buy then sell). After each sell, there is a mandatory one...
Explain Python internals and practices
Answer the following Python deep-dive questions: - Explain the Global Interpreter Lock (GIL) and its impact on CPU-bound vs I/O-bound tasks. - Compare...
Select maximum tasks before deadlines
You are given a set of tasks, each with a positive duration and a deadline (lastDay). You may schedule tasks in any order but only one at a time. Find...
Solve three scheduling and array problems
In this round you are given three separate coding problems to solve. --- Problem 1: Schedule tasks with cooldown You are given: - A list of tasks, whe...