HashMap

A HashMap is a data structure that stores key-value pairs using hashing for fast access, insertion and deletion. Keys are unique and each maps to exactly one value. It offers average O(1) time complexity for basic operations and is widely used for efficient lookups, caching and data mapping in applications.

Top HashMap Blogs

How to Find the Right View of a Binary Tree

Learn how to find the right view of a binary tree using DFS and BFS, with examples, code, complexity analysis and coding interview tips.

Left View of a Binary Tree: DFS and BFS Approaches Explained

Learn how to find the left view of a binary tree using DFS and BFS, with examples, code, complexity analysis, common mistakes and interview tips.

Top View of a Binary Tree Using BFS and DFS | Complete Guide

Learn how to find the top view of a binary tree using DFS and BFS with step-by-step explanations, examples, code, complexity analysis and interview insights.

Bottom View of a Binary Tree: DFS vs BFS Approach

Learn to find the bottom view of a binary tree using horizontal distance. Compares a buggy DFS attempt, a fixed DFS and the optimal BFS solution in Java.

Longest Playlist With No Repeated Songs : Brute Force to Optimal

Find the longest playlist with no repeated songs using brute force, HashSet, and HashMap sliding window techniques, with Java code and dry runs.

What Happens If You Override Equals() but Not GetHashCode() in C#

What are the differences between a Java HashMap and a Hashtable?

How can I iterate over a HashMap in Java?

Popular Topics

Interview

A structured conversation where one participant asks questions and the other provides answers of those questions.

Low-Level Design (LLD)

Low-Level Design (LLD) defines the internal workings of individual software components. It focuses on class structures, object interactions, methods and data flow. LLD translates high-level architecture into detailed designs using principles like SOLID and design patterns, serving as a blueprint for developers to write clean, maintainable and scalable code.

DSA

DSA (Data Structures and Algorithms) is a fundamental concept in computer science that focuses on efficiently storing, organizing and processing data. Data structures like arrays, linked lists, stacks and trees manage data, while algorithms provide step-by-step solutions to problems. Mastering DSA is essential for writing optimized, scalable and high-performance code.

Experienced Candidate Intervie

Experienced Candidate Interview is a hiring process designed for professionals with prior work experience, focusing on advanced technical expertise, real-world problem-solving, system design knowledge, leadership ability and past project impact. It evaluates not only skills but also decision-making, ownership and contribution to business outcomes.

C# (C-Sharp) is a modern, object-oriented programming language developed by Microsoft for building secure, scalable applications. It runs on the .NET platform and supports features like strong typing, garbage collection, LINQ, async programming and cross-platform development. C# is widely used for web, desktop, game development (Unity), cloud services and enterprise-level software solutions.

Query

In databases, a query is a request to retrieve, insert, update or delete data. Written in SQL (Structured Query Language), queries can be simple, like fetching all rows from a table, or complex, involving joins, conditions and aggregations. They are essential for interacting with and managing database information efficiently.

Technical Interview

Technical Interview is a structured assessment where employers evaluate a candidate’s technical skills, problem-solving ability and practical knowledge related to a specific role. It typically includes coding challenges, system design questions, debugging tasks and discussions about past projects. The goal of a technical interview is to measure how effectively a candidate can apply their technical expertise to solve real-world problems.

Coding Problems

Coding problems are exercises designed to test a programmer’s ability to write logic, solve challenges and apply algorithms or data structures. They help improve problem-solving skills, logical thinking and coding efficiency. Common in interviews and competitive programming, coding problems range from simple tasks to complex algorithmic challenges, preparing developers for real-world software development scenarios.

High-Level Design (HLD)

High-Level Design (HLD) outlines the system architecture and overall structure of a software solution. It defines components, modules, data flow, technologies and their interactions. HLD focuses on scalability, performance and reliability, serving as a bridge between requirements and Low-Level Design. It’s essential for planning system-wide decisions.

Java

Java is a high-level object-oriented programming language. it's firstly released by Sun Microsystems in 1995. Use this tag when you're having queries using or understanding the language. This tag is also applicable to Java libraries and frameworks.

Most Popular Tools

Explore our top online tools including a blank page for notes, a QR code generator, word counter and collaborative editor. These free, easy-to-use utilities help you write, analyze, share and organize content faster. Perfect for developers, creators and students to streamline everyday digital tasks efficiently.

Blank Page

Create a blank canvas for your ideas, notes or sketches. Use this tool for rough work and jotting down your thoughts

QR Code Generator

A QR Code Generator is a tool that instantly converts text, URLs or other data into a scannable QR code. Users can create custom QR codes for websites, contact info or messages. It's commonly used for quick access, sharing and printing without needing a backend or complex setup.

Word Counter

Perform various string operations like counting characters, words or letters.

Collaborative Editor

Collab Editor is a powerful, free-to-use online platform that lets you collaborate in real-time. Whether you re working on documents, brainstorming idea, or discussing projects etc