For challenges which involve deciding whether or not the input meets certain criteria, and outputting some data, representing that decision.

In computer science, a decision problem is a problem where a yes-or-no question is posed. These types of problems are at the core of many important open questions in computer science, like the P versus NP problem. These types of problems often make good challenges with simple specifications.

As per our meta consensus, for output, you can choose to

  • output truthy/falsy using your language's convention (swapping is allowed), or
  • use two distinct, fixed values to represent true (affirmative) or false (negative) respectively.