Get the essentials of Big O notation and time complexity – as a free one-page PDF. With it, you’ll always choose the most efficient data structure for the job, walk into technical interviews with confidence, and become known for tackling complex problems systematically.
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This Cheat Sheet is perfect for you if...
… you want to write more efficient code:
and need a better feel for the complexity of your algorithms.
… you are preparing for technical interviews:
and want to refresh the basics of algorithm analysis.
… you are just getting started with algorithms:
and need a quick overview of the most important complexity classes.
I’ve been working with Java for 30 years as a developer, CTO, trainer, author, and speaker – and I’ve made it my mission to help others improve their programming skills.
With HappyCoders.eu, I’ve built one of the most widely read Java blogs in the German-speaking world – including an extensive article series on algorithms and data structures and their time complexity.
100 % of the participants who answered would recommend my training – 82 % without reservation.
A super useful tutorial that actually answered all my open questions.
Both the cheat sheet and the articles explain things simply and clearly – this can save a lot of time otherwise spent slogging through documentation.
Thanks to the English version, also suitable for work; I was able to recommend HappyCoders.eu there, too.
Excellent teacher, explains with detailed images and good code.
The PDF summarizes the essentials of the 7 key time complexity classes on one page – from constant to factorial time.
My blog covers a wide range of Java, software architecture, and performance topics – from foundational concepts to advanced patterns.
If you want to dive deeper, take a look at my trainings: hands-on, easy to follow, and directly applicable to your day-to-day project work. Instead of pure theory, I focus on principles that help you write code that’s better, more maintainable, and more performant in the long run.
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