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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Perform matrix Candy Crush elimination
Question Implement a function that, given an m × n integer matrix representing colored blocks (same integers = same color), performs one round of "Can...
Design test-run logging and query functions
Question Implement log(test_id, timestamp, status) to record a test run, where timestamps are strictly increasing across all test IDs. Implement get_m...
Solve weighted pick and product except self
Question LeetCode 528. Random Pick with Weight LeetCode 238. Product of Array Except Self https://leetcode.com/problems/random-pick-with-weight/descri...
Solve stock trading with pattern rules
Question Given an array of daily stock prices and two pattern arrays: sellPattern and buyPattern, each consisting of 1 (price up) and -1 (price down) ...
Count subarrays with ≥k identical pairs
Question LeetCode 2537. Count the Number of Good Subarrays – Given an integer array nums and an integer k, return the number of contiguous subarrays i...
Implement custom iterator classes
Question In a blank coding environment (no IDE assistance, no autocomplete), implement an iterator abstraction entirely from scratch. The interviewer ...
Find earliest supporting dependency version
Question Given a list of dependency versions (e.g. [103.003.02, 103.003.03, 203.003.02]) and a black-box API isSupported(v), design an algorithm to fi...
Find longest segment with dominant ends
Question Given an integer array nums, find and return the length of the longest contiguous subarray such that the first and last elements of the subar...
Count Word Frequency and Print Top Three Words
Scenario First-round Python coding screening Question Using only basic Python, write a function that receives a list of strings and returns a dictiona...
Optimize Travel Costs and Generate Rotational Symmetric Numbers
Scenario You are building a travel-search engine that must 1) show customers the cheapest round-trip they can book if departure and return prices vary...
Find Smallest Missing Positive Integer in O(n) Time
Scenario LeetCode-style algorithm phone interview Question Implement a function that returns the smallest missing positive integer in an unsorted inte...
Critique Shell Script for Credit-Card Program Tech Round
Scenario Tech round for a new credit-card program: candidate is shown a 5-6 line shell script and asked to critique it Question What kind of file is "...
Implement string and basic ML algorithms
You are given three implementation tasks that mix algorithms and basic machine learning models. --- Task 1: Longest substring with all distinct charac...
Implement basic calculator with four operations
Implement a basic arithmetic expression evaluator. Problem You are given a string s representing a mathematical expression containing non-negative int...
Evaluate arithmetic expression with precedence
Question Implement an evaluator for a string arithmetic expression. The input contains non-negative integers, the operators +, -, `, /, parentheses ( ...
Implement nth Fibonacci number
Problem Write a function that returns the n-th Fibonacci number. The Fibonacci sequence is defined as: - \(F(0)=0\) - \(F(1)=1\) - \(F(n)=F(n-1)+F(n-2...
Find longest unique show window
Given an array of show names (strings) representing a user's viewing history, return the start and end indices of a longest contiguous subarray that c...
Implement zigzag level-order traversal
Given the root of a binary tree, return the node values in zigzag level order: visit nodes level by level, reading the first level from left to right,...
Design time-versioned KV without timestamp argument
Design a time-versioned key-value store that does not accept a timestamp argument on writes. Support set(key, value) which stores the value with an in...
Solve four OA coding problems
The online assessment reportedly contained four coding problems: 1. Compare negative and positive counts Given a sorted integer array nums in non...