alerosa

Hahaha I have no idea how that code works, but looks a MILLION times easier and smarter than what i did in C; mine had like 100 lines or something. Still wondering if there is a smart way to do this.

Phil, this was passed down to me by a teacher in my senior year in high school (I live in Brazil btw ). No one got it then. I've solved it using C, then later using Excel's Solver. Couldn't do it "elegantly", though.

There are 27 spaces that need to be filled with a one-digit number each. Each number from 1 to 9 must be used exactly three times, following this one rule: - Between the spaces which contain the number X, there must be X spaces containing other numbers. For example: 1 _ 1 _ 1 _ 2 _ _ 2 _ 3 2 _ _ 3 _ _ _ 3 _ _ _ _ _ _ _ In the above example, between the first "1" and the second "1", there is one space. Between the second "1" and the third "1", there is one space. Between the first "2" and the second "2", there are two spaces. Between the second "2" and the third "2", there are two spaces, and so on... In the end, all 27 spaces must be filled in with a number from 1 through 9, each number must appear exactly 3 times, and the rule explained above must be respected. Can you prove there is a solution to this? If so, can you find this solution?