Coding & Algorithms Interview Questions
Practice 2,960 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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"Coaches and bootcamp prep courses cost around $200-300 but PracHub Premium is actually less than a Netflix subscription. And it landed me a $178K offer."

"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."
Validate alternating checkout/return logs
Given a chronological list of events logs of the form (timestamp, book_id, is_checkout) where is_checkout is True for a checkout and False for a retur...
Compare heap and stack memory
Compare heap and stack memory. Explain how each is allocated and freed, typical lifetimes of data stored there, access patterns and performance charac...
Solve sliding-window and heap problems
Question Design an algorithm using a sliding window to compute the maximum sum of any contiguous subarray of length k; explain time- and space-complex...
Solve matrix rotation and 1-D illumination
Question LeetCode 48. Rotate Image – rotate an n×n matrix 90° clockwise (extra space allowed). Find the point(s) with the maximum number of illuminate...
Determine Maximum Path Length in Directed Acyclic Graph
Scenario A backend service represents task dependencies as a directed graph; you need to understand how deep the longest dependency chain can get. Que...
Find Minimum Path Sum in Integer Triangle
Scenario Tech interview round 1 – dynamic programming challenge Question Given a triangle of integers, find the minimum path sum from top to bottom. A...
Design Algorithm for Longest Substring with K Distinct Characters
Scenario Tech interview round 2 – sliding-window algorithm Question Design an algorithm that finds the length of the longest substring containing at m...
Detect shuffle-mode sequence
Question Given a playlist of distinct songs and two player modes—Random (each next song chosen independently and uniformly at random, with replacement...
Solve three LeetCode coding problems
Question LeetCode 1249. Minimum Remove to Make Valid Parentheses LeetCode 827. Making A Large Island LeetCode 199. Binary Tree Right Side View https:/...
Randomly partition array into k segments
Question Given a list of integers and an integer k representing the number of segments, write a function that randomly partitions the list into k non-...
Parse password from indexed matrix file
Question Given a filepath to a text file containing one index line [x, y] followed by a matrix of characters (origin at lower-left (0, 0)), return the...
Evaluate dependent variable expressions
Question Given a target variable name and a list of assignment strings of the form 'Ti = expression' where the expression is either a number, a single...
Convert bitmap into ASCII characters
Question Given an array/string of 0-1 bits representing a bitmap font, write code to render each character as a grid using '.' for 0 and '#' for 1, an...
Implement thread-safe blocking queue
Question Design and implement a thread-safe bounded blocking queue that supports concurrent enqueue and dequeue operations using standard synchronizat...
Find most frequent log user
Question You are given a list of log entries in string format, where each entry contains a username and an access timestamp separated by a delimiter (...
Explain strings and copy complexity
Question What is a string? What fields does a struct string contain, and how would you implement it yourself? What is the time complexity of copying a...
Check Palindrome and Add Decimal Strings
Question LeetCode 266. Palindrome Permutation – Given a string, determine whether any permutation can form a palindrome. Follow-up: If a palindrome pe...
Implement right side view and local minimum search
Question LeetCode 199. Binary Tree Right Side View — Given the root of a binary tree, return the values of the nodes you can see ordered from top to b...
Determine minimal substitutions and removals
Question Given a list of words, determine the minimum number of character substitutions required so that, in every word, no two adjacent characters ar...
Find lowest common ancestor
Question LeetCode 236. Lowest Common Ancestor of a Binary Tree — Given a binary tree, find the lowest common ancestor (LCA) of two given nodes. Follow...