LeetCode is described as 'Practice and level up your development skills and prepare for technical interviews' and is an website in the Development category. There are more than 25 alternatives to LeetCode, not only websites but also apps for a variety of platforms, including Windows, Mac, Self-Hosted solutions and Linux. The best alternative is Khan Academy, which is free. Other great sites and apps similar to LeetCode are Codecademy (Freemium), exercism (Free, Open Source), HackerRank (Free Personal) and Codewars (Freemium).
- Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. View 29 alternatives to Project Euler
- Free • Proprietary
Project Euler vs LeetCodeThere is a mathematical focus and has good examples of why some problems need optimized algorithms. You get exposed to a lot of cool math concepts and are challenged to write in efficient time and space complexity.