Every mobile phone has an IMEI number. They're 15 digts in length and use the Luhn algorithm. Make a function in your chosen language that validates IMEI numbers in as few characters as possible. 355555555555550 < valid IMEI 355555555555551 < invalid IMEI

Task: Your challenge is to make a tool that will golf your favorite language. It will take input as a file or stdin, and make it as small as possible. The golfer can be created in any language, and it must be able to golf at least one language (polyglots are ok). Rules: Your program will take...

At the beginning of this year, I created the problem Produce the number 2014 without any numbers in your source code. It exploded in popularity quite unexpectedly, becoming the highest-voted question of all time on this site (as well as the first question on PCG.SE to get more than 100,000 views)...

Can we get a "Too trivial" close vote for questions that would force very similar answers? For example this one: Ration your integers and feed the people After the edit the question allowed only for one single sane implementation of the algorithm and the only thing that would differ is the choi...

Stack Overflow has an interesting 404 not found page: We couldn't find the page you requested. We did, however, find this program. How about something like that for Code Golf?