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."
Design structure for top-K frequent elements
You are working with a large collection of items represented by integer IDs (e.g., product IDs, user IDs, etc.). Updates and queries arrive over time....
Describe Angular features
What are the key features of Angular? Discuss modules, components, templates, dependency injection, change detection, RxJS observables, routing, and f...
Design duplicate-file detection using size
You are given a large POSIX-like filesystem containing millions of files across nested directories. Design an algorithm to find groups of duplicate fi...
Find substring from dictionary concatenation
Given a string s and a dictionary of words dict, determine whether s contains a substring that is exactly a concatenation of one or more words from di...
Process auth requests with fraud rules
Question Implement a function that, given a list of Authorization Requests (timestamp_seconds, unique_id, amount, card_number, merchant), outputs a hu...
Detect earliest collision among moving cars
You are given n vehicles with kinematics parameters. A “collision” means two vehicles occupy the same position at the same time. Assume continuous tim...
Find the nearest city sharing axis
You are given N cities, each with a unique name and integer coordinates (x, y). For any query city, return the nearest city that shares either the sam...
Determine task order with prerequisites
You are given n tasks labeled 0..n−1 and a list of prerequisite pairs (a, b) meaning task b must be completed before task a. Determine one valid order...
Determine string buildability from dictionary
Given a non-empty string s and a list of non-empty words dict, determine whether s can be formed by concatenating words from dict with unlimited reuse...
Design faster delay-time computation
You are given an array of integers representing task priorities. Tasks execute from right to left. For each index i, define its delay time as j - i wh...
Solve a two-jug measuring problem
You are given two jugs with capacities x and y liters and an unlimited water source. You may perform these operations: fill a jug, empty a jug, or pou...
Find top-k frequent elements efficiently
Given an array (or stream) of integers and an integer k, return any ordering of the k most frequent values. Implement a solution using a heap and disc...
Implement deep clone for complex objects
Implement a deep-clone function for nested objects in JavaScript (or a language of your choice) without using JSON serialization or third-party librar...
Compute vertical order of a BST
Compute the vertical order traversal of a binary search tree. Define coordinates so the root is at column 0, row 0; the left child is (col−1, row+ 1) ...
Refactor rock–paper–scissors for config and ties
Refactor an existing Rock–Paper–Scissors tournament with three robot players so that the number of rounds is configurable and the system also tracks t...
Design server allocation for multi-type nodes
Design a service to manage a large pool (about 100, 000) of server nodes. Each node can satisfy multiple instance types; clients call getServer(reqNum...
Design menu DP and optimize for three items
You are given a restaurant menu with n single items and m combo offers. Each single item i has a price p[i] (in cents). Each combo j specifies nonnega...
Implement cocktail shaker sort and analyze
Implement the cocktail shaker sort (bidirectional bubble sort) for an array of integers. Optimize it with early termination and shrinking bounds, and ...
Find shortest path and compare BFS vs DFS
Given an unweighted graph (directed or undirected), explain how to find the shortest path between two nodes without writing code. Describe the algorit...
Solve jumps and anagram-similarity problems
You are given two independent tasks. Task A (Maximize calories over jumps): - There are n blocks with integer heights height[i] ≥ 0. - You start on th...