I have found a few good blog posts with reviews of code exercise websites. However, most of these posts are targeted at either competitive programmers or complete beginners. I am starting a series of posts reviewing the most popular programming exercise sites from the perspective of a programming job candidate.
The first of the series is Project Euler.
Project Euler provides an extraordinary number of code challenges, 608 at the time of writing. However, do not expect classical software engineering challenges such as sorting or binary trees, these katas are purely mathematical. They cover most of the maths concepts that you may find in the shorter whiteboard code exercises such as prime number, Fibonacci sequences or palindromes.
You cannot submit your code online, you need to set up an IDE to solve their exercises. You can submit the result though, and you can track the number of exercises that you have successfully completed. The user interface is good but would be useful if the exercises were organised by difficulty or some sort of tag. It usually takes many clicks to find the right exercise.
In sum, Project Euler let you practice skills tested on a programming job interview but overall I do not think this is an efficient way to approach a code interview.
Overall classification: 3/5
✅ Lots of exercises to choose from.
❌ Not targeted at programming job interviewees.
❌ No online code submissions.
Direct link here