Coding & Algorithms Interview Questions
Practice 3,469 real Coding & Algorithms interview questions for 2026. Covers companies like Meta, Amazon, Google, Uber, and Microsoft. Real questions from actual interviews with detailed solutions — ideal for focused interview preparation. Coding & Algorithms interview questions are the single most common technical gate for software engineering roles and are used to evaluate problem framing, algorithm selection, complexity trade-offs, correctness, edge-case reasoning, and clear communication under time pressure. Expect this category to appear in early technical screens and repeatedly across onsite loops at companies that weight it heavily (notably Meta, Google, and Amazon). Interviews will test arrays and strings, trees and graphs, dynamic programming, hashing and two‑pointer techniques, and the candidate’s ability to test and optimize code in a shared editor. Prepare with timed mock interviews, practice in the same editor you’ll use live, and build a progressive schedule that moves from fundamentals to medium/hard problems; typical candidates invest several weeks to a few months of focused practice depending on seniority and target company.
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Generate all permutations of an array
This question evaluates understanding of permutation generation, recursion and backtracking techniques, along with skills in state-space exploration a...
Implement cd and merge intervals
This question evaluates proficiency in filesystem path normalization (string parsing, tokenization, and edge-case handling) and interval-merging algor...
Add Two Forward-Order Lists
This question evaluates linked list manipulation and numerical addition represented in forward-order digit encoding, testing competency in handling di...
Count paths with prime-ending jumps
You are given an integer n representing the top of a staircase, where you start at step 0 and want to land exactly on step n. In one move, you may jum...
Detect Trigger and Resolve Events
You are given transaction logs sorted by non-decreasing timestamp. Each log record has four fields: - timestamp: integer time in seconds - merchant_id...
Count unique Morse-code word transformations
Given an array of lowercase strings words. Each letter 'a' to 'z' has a corresponding Morse code string (standard 26-letter mapping). A word’s transfo...
Find best-matching binary pattern with wildcards
This question evaluates pattern-matching and string-algorithm skills, including handling wildcards and variable-length matches, priority-based rule se...
Convert a PDF to a CDF
Given a continuous random variable X with probability density function f(x), write code or describe an algorithm to construct its cumulative distribut...
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 ...
Decode Ambiguous Morse Messages
You are given a mapping from Morse patterns to lowercase English letters. Implement two related functions: 1. Deterministic decoding with character an...
Count substrings and generate TOC
Solve the following two coding problems. 1. Count valid binary substrings Given a string s consisting only of '0' and '1', count how many substrings s...
Can two names match with ≤2 swaps?
You are given two restaurant names represented as strings s and t of equal length (same character set, case-sensitive). In one operation, you may swap...
Design a circular queue data structure
This question evaluates understanding of circular buffer data structures and the ability to implement fixed-capacity queue operations with O(1) time a...
Find dictionary words matching a phone digit string
This question evaluates familiarity with phone-keypad character-to-digit mappings, string pattern matching, and efficient filtering of dictionary word...
Solve common array/graph interview problems
This multi-part question evaluates proficiency in array and matrix manipulation, graph traversal and shortest-path reasoning for word transformations,...
Implement Jackknife and Random Choice
This question evaluates understanding of statistical resampling (jackknife), probabilistic sampling algorithms including with- and without-replacement...
Implement an event emitter
This question evaluates understanding of event-driven programming and API design in a frontend environment, specifically the ability to manage event l...
Find top/bottom-k words in list or stream
You are given words (strings) either as a finite list or as an unbounded stream. 1) List version: Given an array words and an integer k, return: - the...
Implement stack variants and upward path sum
Question Answer the following coding questions. They progress from augmented stacks to streaming statistics to tree path reasoning. 1. MinStack — Desi...
Estimate Two Conditional Win Probabilities by Simulation
Estimate Two Conditional Win Probabilities by Simulation You are given a game with three closed doors, labeled 0, 1, and 2. Behind exactly one door is...