If you’re learning to write code to bring your startup idea to life, check out these excellent coding practice sites to help you stay on top of your game.

/r/dailyprogrammer

Every week, you’ll get one easy, medium, and hard coding practice challenge. You can post your solution and compare notes with other users on the subreddit. At 122,000 subscribers, you won’t ever be solving the problems alone.

Project Euler

From the site:

Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems.

These get hard really quick, so don’t get discouraged if you hit a wall. You probably don’t need this level of math proficiency to build most apps. If you can solve these coding practice problems, you can work through just about any problems you come upon developing your app.

Coderbyte

Coderbyte and the subsequent sites on the list are of a different breed which allow you to code your solutions and have them automatically evaluated on the site. Where dailyprogrammer and Project Euler have you submit solutions to be evaluated by other users, Coderbyte lets you write your solution in one of a number of languages and test them immediately.

View suggested solutions and read explanations of them. You can still discuss your solutions with others on the site just like you can on dailyprogrammer and Project Euler, but the addition of immediate feedback makes coding practice more gratifying.

HackerRank

HackerRank gives instant feedback just like Coderbyte. The editor has some neat features (like Vim and emacs modes), but those will only become interesting as you become a more accomplished developer.

What’s most interesting about HackerRank is the way it divides exercises into tracks. These allow you to focus your coding practice around a specialized skill, language, or core competency.

It has a competitive layer in which you try to attain the highest “rank” among all the users of the site. They optionally use this rank to show you to potential employers. Not useful to founders but an interesting feature nonetheless.

CodeFights

CodeFights has a healthy slathering of gamification. As with the others, you do practice exercises and receive feedback immediately. Each completion earns you points that contributes to an overall score. You’ll get game-like achievement popups as you move through your challenges which will track your progression.

It offers several “modes” (again, like a game) including races against other users, daily and weekly coding challenges, and tournaments.

It’s probably the best looking of the six profiled here too!

Codewars

Codewars focuses only on Python and Javascript, which are two languages you’ll find very useful in building your startup. Not as flexible as some of the others, though, which offer a plethora of languages.

It puts other users’ solutions to the problems front-and-center, displaying them after you complete an exercise. It groups similar solutions together and orders them by how many people submitted the same solution. This makes it really easy to pick up language features you weren’t aware of. Usually, good solutions will rise to the top. You can compare these to yours to find out how you can improve your solution.

Which Site Is Best for Coding Practice?

Codewars combination of instant feedback with a focus on comparing solutions puts it on top. The instant feedback allows you to keep momentum up where you might have to wait for feedback with dailyprogrammer or Project Euler. However, showing others’ solutions highlights the opportunity to learn from other users like the aforementioned sites.

It’s not the prettiest. It doesn’t have the coolest game-like scorekeeping and achievement systems. Despite that, the value of focusing on other solutions cannot be understated when you’re learning to build your startup.