LeetCode

LeetCode is an online platform and community that provides a large collection of programming problems and an automated judge to help users practice coding and prepare for technical interviews. The site supports multiple programming languages, including Python, Java, C++, JavaScript, Go, and others. Problems are organized by topic (such as arrays, trees, dynamic programming, and graph theory), difficulty (Easy, Medium, Hard), and often by company-specific question sets.

LeetCode features an online editor and a judging engine that compiles and runs user submissions against test cases, returning results and performance metrics. Users can view official solutions, study examples, and discuss approaches in the LeetCode Discuss forum. The platform also offers mock interviews, timed challenges, and weekly or biweekly contests to simulate real interview conditions.

LeetCode Premium is a paid tier that unlocks additional problems, curated study plans, and company-specific question banks. Premium content often includes premium-only explanations, video solutions, and enhanced filtering to target topics or roles. The overall aim is to help learners build problem-solving skills and demonstrate proficiency to potential employers.

Impact and community: LeetCode is widely used by software engineers to prepare for interviews at large tech companies and startups alike. It also serves as a community hub for sharing strategies and solutions, and hosts regular contests that provide benchmarking and motivation for practice.