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."
Fetch paginated data from two APIs
Write a function get_enriched_records(api_a_url, api_b_url). api_a_url returns paginated JSON in the form: `json { "data": [ {"id": 1, "ref_id":...
Implement a serializable key-value store
Implement in C++ an in-memory key-value store with: - put(key: string, value: string), get(key) -> optional<string>, erase(key). - serialize() -> vect...
Find two numbers that sum to a target
Array sum lookup Given an integer array nums and an integer target, find two distinct indices i and j such that: - nums[i] + nums[j] == target - i != ...
Implement Order Modification Feature
You are given an existing C++ trading system with a client/server architecture. The current system already supports two request types: - AddOrder(orde...
Implement monotonic-array linear interpolation
Question Implement a function interpolate(array_x, array_y, x) that returns the linearly interpolated y-value for a query x-value, given paired data p...
Flatten nested JSON into a string map
Problem You are given an input JSON object that may contain nested objects and arrays. Your task is to flatten it into a single-level key/value mappin...
Print a Centered Pascal Triangle
Given a positive integer height, generate the first height rows of Pascal's triangle and print them as a centered text triangle. Formatting requiremen...
Maximize watch time under adjacency constraint
You are given a sequence of videos in a feed. - Input: - An integer array duration[1..n], where duration[i] is the length of video i in seconds. -...
Implement memcpy with misaligned addresses
Implement a C-style memcpy that correctly handles misaligned source/destination addresses. Task Write a function: `c void my_memcpy(void dst, const vo...
Solve these string, subset, and date problems
You are asked to solve multiple coding tasks. 1) Reverse word order in a string - Input: a string s containing words separated by spaces (may contain ...
Solve classic coding interview problems
Solve the following algorithmic problems: 1. Egg testing with limited resources: You are given k identical eggs and a building with n floors. An egg b...
Compute longest increasing subsequence length
Coding Question You are given an integer array nums. Return the length of the longest strictly increasing subsequence (not necessarily contiguous). A ...
Design hit counter for last 5 minutes
You are launching a new webpage and need a last-minute server-side metric to track popularity in real time. Implement a hit counter that supports the ...
Solve three C++ algorithmic tasks
Solve the following three C++ algorithmic tasks. For each, implement an efficient function and state time and space complexity. a) Diminishing prices ...
Simulate and Construct Tournament Rankings
You are given a single-elimination tournament represented by an array of ranks. The array is a permutation of the integers 1..n, where a smaller numbe...
Implement Stratified Sampling by Country
You are given a large in-memory Python list named records, where each element is a dictionary with at least the following keys: - country: str - devic...
Build a Pivot Table Aggregator
Implement a function that builds a pivot table from a list of records. Each record contains a row_key, a column_key, and a numeric value. Requirements...
Solve Union-Find, Graph, and Stream Problems
Solve the following independent coding problems. 1. Merge Product Categories You are given a list of tuples (productA, productB). Each tuple means the...
Compute bus-on-time and dice-sum probabilities
You are asked two basic probability questions. A) Catching a bus to arrive before a movie A person is going to the cinema. The movie starts in L minut...
Bracket substrings matching any pattern
Problem You are given a sentence s (words separated by single spaces) and a list of strings patterns. For each word in the sentence, if the word conta...