leetcode is similar to the hackerrank website, it's a set of about 700 programming problems where one can enter a solution in almost any programming language applicable (there are some SQL queries). There is also a discussion forum for each question. Occasionally there is more writing by the problem creator with alternate solutions listed. I've found a few companies use the hackerrank for initial programming tests, I kind of dislike hackerrank because alot of the hackerrank tests rely on stdio input equivalent in each language which in some languages I never use in real life, i.e. I never use the Java command line prompt except for fooling around on hackerrank and some of the questions on hackerrank are ridiculously obtuse - I've skipped to the discussion and find that is the number one upvoted type of comment more than once.