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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"I honestly don't know how you guys gather so many real interview questions. It's almost scary. I walked into my Amazon loop and recognized 3 out of 4 problems from your database."

"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."
Compute weighted sum of nested lists
Given a nested collection that can contain integers or other nested collections, compute the depth-weighted sum where each integer is multiplied by it...
Contrast TCP vs UDP; detect loss
Contrast TCP and UDP in reliability, ordering, congestion control, connection setup, and overhead. How does TCP detect packet loss and trigger retrans...
Debug round-robin, DashMap, and simple cache
You are given a service that routes requests to a list of nodes, each marked as either available or unavailable. The pickNode() function is intended t...
Find all anagram start indices
Problem Given two strings s and p, return all starting indices of substrings in s that are anagrams (permutations) of p. Input - s: string - p: string...
Handle invalid Lisp expression parsing
Question LeetCode 736. Parse Lisp Expression – Given a string representing a Lisp-like expression containing let/add/mult operations and variable bind...
Delete duplicate files via DFS
Question LeetCode 609. Find Duplicate File in System – Implement an algorithm (using DFS/backtracking) to delete files with duplicate content in a fil...
Solve palindrome pairs and key path
Question LeetCode 336. Palindrome Pairs; LeetCode 864. Shortest Path to Get All Keys https://leetcode.com/problems/palindrome-pairs/description/ https...
Pivot order-status counts
Question Given an orders table (order_id, shopper_id, order_date, status, …), pivot the data so that each row is one shopper and each column shows the...
Solve tree distance and design file system
Question Given a binary tree, find the maximum distance between two 'alive' nodes, where 'alive' nodes are initially the leaves; follow-up: allow the ...
Merge overlapping intervals
Question LeetCode 56. Merge Intervals – Given a collection of intervals, merge all overlapping intervals into one and return an array of the non-overl...
Solve Rotting Oranges and Bus Walk Reachability
Question LeetCode 994. Rotting Oranges. 2) Given start and end grid coordinates, an integer k (maximum walking distance), and a bidirectional graph of...
Determine most popular concert city
Question Given a set of concert venue vote records, determine which city is the most popular. How would you normalize city names that have multiple sp...
Find Lowest Common Ancestor with Parents
Question LeetCode 1650. Lowest Common Ancestor of a Binary Tree III Compute the time and space complexity of your solution https://leetcode.com/proble...
Solve UTF-8 Validation & Shortest Path
Question LeetCode 393. UTF-8 Validation LeetCode 1091. Shortest Path in Binary Matrix https://leetcode.com/problems/utf-8-validation/description/ http...
Implement Python Function for Longest Unique Substring Length
Scenario Real-time text analytics service enforcing uniqueness constraints Question Implement a Python function returning the length of the longest su...
Simulate Coin Flips to Determine Fairness via Empirical Distribution
Scenario You must test whether a coin is fair by simulation. Question Write code that repeatedly simulates n coin flips, records the number of heads, ...
Design Efficient Data Structure for Median Retrieval
Scenario Senior problem-solving round assessing algorithmic thinking under time pressure. Question Design a data structure that supports inserting int...
Implement and Analyze 'Merge k Sorted Lists' Algorithm
Scenario Algorithm coding challenge during the final interview round. Question Implement LeetCode 23 ‘Merge k Sorted Lists’ and explain your complexit...
Optimize Driver Repositioning for Minimal Pickup Time
Scenario Design and implement algorithms for ride-sharing dispatch and capacity planning. Question Given historical rider demand density and current d...
Optimize Oculus Data Streaming with Bandwidth Constraints
Scenario Algorithmic screening for Meta VR/AR teams covering Oculus data streaming and geometric optimization. Question Oculus: Given an array frame_s...