Improve Coding Skills by testing these websites :
The HackerRank Community is one of the largest learning and competition community for programmers. They have exercises related to Python, Java, SQL, C++, Linux Shell and lots more. You will be able to learn new programming topics and techniques by going through the challenges on HackerRank.
HackerEarth is an online skill assessment tool for conducting programming tests to evaluate developers. Supports almost all famous programming languages.
CodeChef was created as a platform to help programmers make it big in the world of algorithms, computer programming, and programming contests.
Exercism is another tool to level up your programming and coding skills. Exercises are suitable for both code newbies and experienced programmers. You can download and practice problems over 30 different programming languages.
Codeforces is a Russian website dedicated to competitive programming. They provide a different mode of services like — participation in the short (2-hours) contests, challenge/hack other contestants solutions, ability to solve problems from previous contests for training purposes and many other.
6. Sphere Online Judge (SPOJ)
SPOJ (Sphere Online Judge) is an online judge system with over 200,000 registered users and over 20,000 problems. Tasks are prepared by its community of problem setters or are taken from previous programming contests.
CodingBat is a free site of live coding problems to build coding skill in Java and Python. CodingBat problems work great as homework, or for self-study practice, or in a lab, or as live lecture examples.
8. Project Euler
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.
CodeEval is a platform used by developers to showcase their skills. Developers can participate in app building competitions and win cash/prizes. They can also solve programming challenges as a way to impress employers with their technical skills.
Topcoder is one of the world’s largest community of competitive designers, developers, and data scientists. Topcoder hosts fortnightly online competitive programming competitions.
11. Google Code Jam
Google Code Jam is an international programming competition hosted and administered by Google. The competition consists of a set of algorithmic problems which must be solved in a fixed amount of time.
12. LeetCode Online Judge