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."
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Solve binary-search knapsack & graph shortest path
Question Given a sorted list of items, design an efficient solution (using binary search) to achieve the target objective instead of a dynamic-program...
Solve movie ratings, array, release scheduler
Question This is a three-part coding screen used for a Data Scientist role at DRW. You will work through three independent array/sequence problems, ea...
Construct tree from inorder & postorder
Question LeetCode 106. Construct Binary Tree from Inorder and Postorder Traversal – Given the inorder and postorder traversal arrays of a binary tree,...
Determine Length of Longest Unique Substring
Scenario Online assessment: coding portion that follows the SQL questions. Question Implement a function that, given a string s, returns the length of...
Simulate Radioactive Decay to Validate Analytical Solution
Scenario Same radioactive-decay problem, but now validate the analytical answer via simulation during the interview. Question Share screen and write r...
Implement Cosine Similarity Function for String Vectors
Scenario Technical phone screen in Python; assess ability to implement similarity metric. Question Implement a Python function that computes the cosin...
Implement scaled dot-product attention
Task In this interview you are asked to hand-write the forward pass of attention from the mathematical formula (no need to run code). Implement single...
Select the best dasher for an order
You need to assign an order to a dasher. Input: - An order with a pickup location (x, y). - A list of dashers, each with: - id - current location ...
Parse Requests and Compute Balances
You are given an array of strings representing requests in a social payments application. Process the requests in order and return the final balance o...
Count invalid nodes in a BST
You are given the root of a binary tree. A valid Binary Search Tree (BST) must satisfy: for every node with value v, all values in its left subtree ar...
Count players reaching end with moving watchers
You are given a 1D line of L cells indexed 0..L-1. The end cell is L-1. There are: - W watchers with initial integer positions watchers[]. - P players...
Minimize Total Assignment Distance
You are given the coordinates of n analysts and m field devices on a 2D grid, where 1 <= n <= 10 and n <= m <= 15. Each analyst must be assigned exact...
Determine if chasing points will meet
You are given N points in 2D, indexed 0..N-1, forming a cycle. - At time t = 0, point i is at coordinates (xi, yi). - All points move simultaneously a...
Implement IPv4 and CIDR iterators
Problem: IPv4 / CIDR Iterator You are building utilities to iterate through IPv4 addresses. Definitions - An IPv4 address is in dotted decimal form: a...
Find nearest common manager for multiple employees
Given an organizational hierarchy modeled as a rooted tree, build the tree from (employee, manager) pairs and implement a function that, for k ≥ 2 emp...
Find longest substring without repeating characters
Problem Given a string s, find the length of the longest contiguous substring that contains no repeated characters. Input - A string s (may contain le...
Implement a uniq-like function
Implement a function similar to the Unix uniq utility. You are given a sequence of strings representing lines of text in the order they appear in a fi...
Design LRU cache and pick k closest points
1) Design a fixed-capacity in-memory cache that evicts the least recently used key when full. Support get(key) and put(key, value) in O( 1) average ti...
Optimize repeated-value vectors and compute exclusive times
You are given two separate coding tasks from an interview. Task 1: Optimize storage for vectors with repeated values, then compute dot product You are...
Find target using robot movement API
You control a robot in an unknown 2D grid. The grid layout and boundaries are unknown, and you cannot access the map directly. Some cells are blocked ...