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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Compute shared free time intervals
You are given schedules for multiple employees. schedules[i] is a list of busy intervals for employee i, where each interval is half-open [start, end)...
Remove minimum parentheses to balance string
Given a string s containing lowercase letters and the characters '(' and ')', remove the minimum number of parentheses so that the resulting string is...
Design an in-memory file system with limits
Design and implement an in-memory hierarchical file system. Requirements: 1) addFile(String path): Given an absolute path like "path/to/somewhere/file...
Determine string buildability from dictionary
Given a non-empty string s and a list of non-empty words dict, determine whether s can be formed by concatenating words from dict with unlimited reuse...
Find max-score path in weighted DAG
You are given a directed acyclic graph (DAG). Each node v has a score w(v). Each directed edge (u→v) has a nonnegative time cost t(u,v). There is a un...
Find >n/3 elements in sorted array
Question Given a sorted (non-decreasing) integer array A of length n, return all distinct values that occur strictly more than n/3 times. Design an al...
Plot ASCII chart for time-price pairs
Given an unsorted array of (timestamp, price) integer pairs, write a function to render an ASCII chart of the time series. The x-axis must include eve...
Design a coupon redemption system
Implement an in-memory coupon service supporting: addCoupon(code, discount, expiresAt, totalLimit, perUserLimit); redeem(userId, code, now) -> success...
Find grid cell minimizing sum distances
You are given an m x n 2D grid with k marked points. Movement is allowed in four directions (up, down, left, right) with unit cost per step. Find a gr...
Count connected delivery zones
Given an m x n grid representing a service area, each cell is either 'Z' (deliverable zone) or '#' (blocked). Two 'Z' cells belong to the same zone if...
Determine equality of arbitrarily nested sets
Implement a function that determines whether two arbitrarily nested sets are equal. Sets are unordered and contain no duplicates; elements can be inte...
Detect cycles and order with DFS
You are given a directed graph of package dependencies represented as an adjacency list: Map<String, List<String>> deps where deps[p] lists packages t...
Implement merge-in-place and group cyclic-equivalent strings
You are given two ascending arrays to merge in place and a separate grouping task: Part A — In-place merge without known sizes: - Array A contains sor...
Design a nested transaction store
Implement an in-memory key–value store that supports nested transactions with the operations: SET key value, RETURN key, BEGIN, APPLY (commit current ...
Design circular sliding-window ratio tracker
You are given a circular binary array A of length n (A[i] ∈ {0,1}) and a fixed window size w (1 ≤ w ≤ n). Define r (i) as the fraction of 1s within th...
Implement multi-part cost calculator
You are given a price catalog and a list of orders. Implement the following in any language (Python examples acceptable): Inputs - price_catalog: mapp...
Generate split-stay pairs efficiently
Given N Airbnb listings, each with available days as integers, and an inclusive requested date range [L, R], return all ordered pairs (X, Y) of distin...
Find longest palindromic substring
This question evaluates knowledge of string algorithms and pattern recognition, focusing on identifying palindromic substrings and reasoning about tim...
Implement a Weighted Eviction Cache
This question evaluates proficiency with data structures and algorithmic design for resource-constrained caching, specifically weight-aware eviction p...
Maximum Profit from Dated Stock Trade Records
Maximum Profit from Dated Stock Trade Records You are given a log of stock trades. Each trade is a record [date, symbol, price]: - date — a calendar d...