Advent of Code vs LeetCode

Choose Advent of Code if…

• Programmers who like puzzles and want seasonal practice in any language
• Completely free, with every past year's puzzles still available
• Use any language and your own tools

Choose LeetCode if…

• Developers preparing for algorithm-heavy technical interviews at tech companies
• You need iOS and Android, which Advent of Code doesn't list
• Huge problem library with an in-browser judge for many languages
• Free weekly and biweekly contests with a public rating

What is Advent of Code?

Advent of Code is a yearly event run by Eric Wastl since 2015. Each December a new two-part programming puzzle unlocks every day, wrapped in a light story, and you solve it with whatever language and tools you like on your own computer, then submit just the answer. Each player gets their own puzzle input, and every problem is designed to run quickly even on old hardware. People use it for interview prep, learning a new language, team training or friendly races on private leaderboards; the global leaderboard was removed after ten years. Past events stay online, so you can work through the archive at any time of year. It's free to play, supported by sponsors and optional AoC++ donations. It suits programmers who enjoy puzzles; the trade-off is that it runs only once a year and offers no hints, editor or test runner on the site.

What is LeetCode?

LeetCode is the site most software engineers end up on when they start preparing for technical interviews. It hosts a large library of data structure and algorithm problems, plus SQL and shell questions, each with a browser code editor that runs your solution against hidden test cases and reports whether it passed. Problems are tagged by topic and difficulty, and community discussion threads collect alternative solutions. Weekly and biweekly contests give a rating that tracks progress over time. The free account covers most problems, contests and community solutions. Premium, sold as a monthly or annual subscription, adds locked questions, official write-ups, filtering by the companies that asked a question, mock interviews and faster judging. It runs on the web with mobile apps for reading and practising. The focus is narrow: it drills interview-style puzzles rather than teaching programming from scratch, so beginners usually pair it with a course.