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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Implement a Database Connection Pool
This question evaluates skills in concurrent resource management, synchronization primitives, and robust connection lifecycle handling within database...
Find Kth Smallest in BST
You are given the root of a binary search tree and an integer k. Return the value of the node that would appear in the kth position if all node values...
Traverse an Org Chart by Level
You are given an organization's reporting structure as a flat list of employee-manager relationships. Exactly one employee is the root (the CEO) and h...
Swap kth-from-end node with head
Given the head of a singly linked list and an integer k, swap the k-th node from the end with the head node, using O(1) extra memory. Requirements: - ...
Implement lossless dictionary encoding and decoding
Dictionary encoding is a lossless compression technique for a list of tokens. You are given an input string consisting of words separated by commas, e...
Find First Prefix-Matching Word
This question evaluates proficiency in string processing and prefix-matching within arrays, testing the ability to identify the first occurrence and h...
Implement an LRU cache
Design a key-value cache with a fixed capacity. It must support: - get(key): return the value for the key if it exists, otherwise return -1. - put(key...
Minimize Total Assignment Distance
You are given the coordinates of n analysts and m field devices on a 2D grid, where 1 <= n <= 10 and n <= m <= 15. Each analyst must be assigned exact...
Implement cache and merge intervals
This question evaluates proficiency in designing and implementing efficient data structures (a fixed-capacity LRU key-value cache) and interval-proces...
Implement Matrix Move and Logger
This question evaluates array manipulation and in-place algorithm design for handling overlapping submatrix moves, along with data-structure and time-...
Maintain a Stream Median
This question evaluates the ability to design and implement efficient online data structures and algorithms for maintaining dynamic order statistics a...
Solve Signature, File, and Queue Problems
Solve the following interview-style problems: 1. Function signature matching You are given a registry of function definitions. Each function has an...
Determine Reporting Relationships
Build an in-memory organization model that supports three operations on employee IDs: 1. add_manager(a, b): employee a is the direct manager of employ...
Implement Calendar, Tokenizer, and Meeting Optimizer
This question evaluates competencies in interval scheduling and overlap detection, custom string tokenization and parsing rules, and combinatorial opt...
Solve two interview coding problems
This question evaluates graph traversal and pathfinding with weighted edge composition for currency conversion reachability, and sequence partitioning...
Find Kth Largest and Tree Ancestors
In a technical phone interview, the candidate was asked two coding problems in the same round: 1. K-th largest element in an array Given an unsor...
Find Duplicate Files by Content
You are given a list of directory descriptions. Each description has the following format: root_directory file_name_1(content_1) file_name_2(content_2...
Solve Expression and Tree-List Problems
This question evaluates competency in string expression generation under a custom left-to-right evaluation rule and in-place binary search tree manipu...
Generate All Well-Formed Parenthesis Strings
A string of parentheses is called well-formed if every opening bracket ( has a matching closing bracket ) and the brackets are correctly nested. For e...
Find Maximum Rectangle in Bar Chart
Given an array heights of n non-negative integers, where each value represents the height of a vertical bar in a bar chart and every bar has width 1, ...