Coding & Algorithms Interview Questions
Practice 3,429 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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Elements Occurring More Than n/3 Times in a Sorted Array
This question evaluates a candidate's ability to design frequency-counting algorithms over sorted arrays, testing knowledge of majority-element patter...
Find invalid transactions in time-sorted input
Problem You are given a list of transaction records, already sorted in non-decreasing order by time. Each transaction is a string in the form: "name,t...
Match readings with latest same-city humidity
Problem You are given two time-sorted lists of sensor readings: - Temperature records: (time, city, reading) - Humidity records: (time, city, reading)...
Top-K Largest Elements in Every Sliding Window
This question evaluates the ability to design and maintain an ordered data structure that efficiently tracks the top K largest values within a moving ...
Find the Index Range of a Target in a Sorted Array
This question evaluates a candidate's grasp of binary search and its adaptation to locate boundary positions within a sorted array. It tests the abili...
Reconstruct itinerary with lexicographic ties
You are given m airline tickets as directed pairs [from, to]. Build an itinerary that starts at a specified airport start (e.g., "JFK") and uses every...
Count Squares from Points in the Plane
Implement count_squares(points). Given distinct 2D points with integer coordinates, count the unique squares whose four corners all occur in the input...
Implement a Stateful Search Autocomplete Session
Implement a Stateful Search Autocomplete Session Build an autocomplete engine from historical sentences and their usage counts. While a user types a s...
Determine Whether P's Position Is Unique
You are given an R x C rectangular grid and a set of named entities. Each entity must be placed in exactly one distinct cell. You are also given a col...
Find a Canonical Shortest Round Trip Through Flights
Find a Canonical Shortest Round Trip Through Flights Problem Implement shortestRoundTrip(flights, start) -> route. Each element of flights is a direct...
Grid Robot Command Simulator
This question tests practical coding ability by requiring implementation of a command-driven state machine on a bounded 2D grid. It evaluates simulati...
Least Frequently Used (LFU) Cache
This question tests practical data structure design by requiring an O(1) implementation of a Least Frequently Used cache with tie-breaking by recency....
Mark and Compact a Heap-Indexed Subtree
Mark and Compact a Heap-Indexed Subtree An interview report describes an array-encoded tree, marking a target and its descendants with -1, then moving...
Design Composable Event Recommendations
This question evaluates a candidate's ability to design composable, extensible recommendation logic and ranking for a ticket marketplace, emphasizing ...
Compute the Final Robot Score
This question evaluates data structure and algorithm proficiency, focusing on managing dynamic multisets with priority-based selection and reasoning a...
Implement a crash-resilient LRU cache
Implement an LRU-based memoization helper with behavior similar to a standard Python LRU cache. You are given an interface like this: `python class LR...
Optimize CUDA GEMM with tiling and coalescing
CUDA Execution Model, Memory Hierarchy, and GEMM Kernel Design You are interviewing for a Data Scientist / GPU-software role at NVIDIA. The interviewe...
Count Requests Dropped by Multiple Time Windows
Count Requests Dropped by Multiple Time Windows Implement count_dropped(timestamps) for nondecreasing integer seconds. For zero-based request index i,...
Keep At Most K Copies in a Sorted Array
Keep At Most K Copies in a Sorted Array Implement dedupe_sorted(nums, k). Modify the sorted input array in place so each distinct integer appears at m...
Compress Consecutive Characters with Run Lengths
Compress Consecutive Characters with Run Lengths Implement compress_runs(s) and return the compressed string. The input contains ASCII letters only. S...