Rakuten uses Codility to test candidates. After applying for the job, a link to the test was sent to me. The test could be taken anytime within a week, and I had an hour to solve the problem once the test starts. There were various languages that can be chosen from (C was not included).

I think it’s better to get familiar with the online test platform prior to the test, because you only get an hour. And I think posts reviewing helps. It seems to have a set of problems that Rakuten has been using for years. For example, the rectilinear rectangles problem is mentioned multiple times in the posts. The problem I had was not the rectilinear rectangles problem, but was also mentioned in one of the posts.

A problem that was mentioned in one of the posts. A problem about the binary representation of a number.