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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"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."
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Compute max coins with 3-step token moves
You are given a one-dimensional board with n positions represented by a string s of length n: - . = empty cell - T = token - C = coin You may move tok...
Assign bookings to minimum tennis courts
This question evaluates interval scheduling and resource-allocation competencies, testing algorithmic and data-structure knowledge for handling time-i...
Find top-5 most similar rows across datasets
You are given two datasets with the same feature columns: - source (rows you want to match): - source_id (STRING/INT) - f1...fk (NUMERIC; may cont...
Design cache with least-recently-used eviction
You are asked to design an in-memory key–value cache that supports a least-recently-used (LRU) eviction policy. The cache must support the following o...
Rank queries by prefix, frequency, and time
You are given three arrays of the same length n: - queries[i]: a non-empty string representing the text of the i-th query. - timestamps[i]: an integer...
Implement minimal-cost overtime/contractor allocation
You must cover H extra engineering hours this week at minimum cost using employee overtime and optional contractors. Each employee i has a maximum ove...
Implement percentage RMSE and bootstrap its CI
Given a CSV with columns [country, actual_revenue, predicted_revenue], define percentage RMSE as pRMSE = sqrt(mean_i((pred_i/actual_i − 1)^2)). a) Imp...
Solve two-sum variants at scale
Base task: Given nums = [3, 1, 2, 2, 4] and target = 4, return the 0-based index pair (i, j) with i < j such that nums[i] + nums[j] = target. If multi...
Implement an LRU cache with O(1) ops
Design and code an LRU cache supporting get(key) and put(key, value) in O(1) average time with capacity N. Specify your data structures, handle update...
Classify relationships for multiple circle pairs
Given an array pairs of N circle pairs, where each circle is (x, y, r) with integer coordinates and r ≥ 0, classify each pair into one of: IDENTICAL (...
Maximize outfits with distinct colors
You're given counts of items by color; each outfit must contain exactly 3 items, all of distinct colors. You cannot reuse items. Input formats: either...
Implement longest increasing subarray with one deletion
Given an array of integers nums, return the length of the longest strictly increasing contiguous subarray you can obtain by deleting at most one eleme...
Implement max profit with K transactions (DP)
Given an array prices[0..n-1] of daily stock prices and an integer k, implement a bottom-up dynamic program to compute the maximum achievable profit w...
Generate primes up to n efficiently
Implement a function that returns all prime numbers in the inclusive range 1..n. Requirements: handle n up to 10^7 efficiently (time and memory); retu...
Compute array modes with ties and no-mode rule
Write a function that returns the mode(s) of an integer array. Requirements: if all values are unique, return an empty list (there is no mode); allow ...
Implement multiplication without using the multiplication operator
Implement int multiply(int a, int b) without using * or /. You may use +, −, bitwise operators, and shifts. Requirements: - Handle negatives, zero, an...
Implement longest subarray summing to k
Given an integer array nums (length ≤ 200,000; values may be negative) and integer k, return the maximum length and the [l, r] indices of a contiguous...
Detect sequence rule and repair anomaly
Implement next_value(seq: list[int]) that detects the rule of a numeric sequence and returns a tuple (model_name, parameters, anomaly_index_or_None, n...
Implement sliding-window rate limiter with dual thresholds
Implement getRequestStatus(urls: List[str]) -> List[str]. The i-th entry in urls represents a single incoming request at timestamp t = i seconds (t st...
Implement streaming k-way merge with constraints
Implement a function merge_k(iterators, N) that returns the first N items of the global ascending order from k sorted, potentially unbounded iterators...