Saturday, April 11, 2015

Google Codejam 2015 Qualification Round : Part 1: D small in Emily

It's another google codejam qualification round and honestly, these rounds are getting old. We are supposed to spend a whole day solving problems, between the too easy Small inputs and the impossible Large inputs. And what for? Once you get enough points for the cut-off it's not worth it. Unless you planned to be connected at 19:00 and try to solve the problems as fast as possible, then your rank might actually mean something...

One time I had position 29 at a qualification round. Impressive! Except it's all fake. I didn't even qualify to the third round that year.

I actually might have some rants to make about the formats used in our competitions. Did you know that google found winning programming competitions is correlated with bad work performance? It's SCIENCE. (Supposedly). Although us fans of these contests might like to think there is some sort of mistake in this result of Google's data mining. We cannot just really say it's not true, without doing any actual analysis of the data used and how the conclusion was made.

Anyway, so I want to qualify to round 1, but I was bored of qualifications rounds. So I decided to make them interesting by doing something different to my routine of using c++ and trying to get a perfect score. Instead, I wanted to make special language choices. Use only languages that I designed myself or that I didn't actually learn before the day of the round.


Once I decided to use special languages. I knew that one of the languages to use today was Emily. It's a relatively new languages, so that's a bonus. Also because o> f luck I've been seeing many previews of its development and finding them interesting. Honestly tho I kind of made this decision without thinking a lot...

The day of the round I noticed I should start learning this language. I figured out a couple of issues. Emily doesn't seem to have a way to read input. Fortunately, it does have the ability to write things. Unfortunately, only strings that you cannot process or floats. For some reason, Emily in its 0.1 version only has floating point numbers. That was going to be a bit of a problem.

My initial plan was to only use Emily and the language I will mention next; and hope to advance using only them. *After* getting an advancing score, I could actually try to use other languages just for fun. When I opened the problems, this seemed difficult. All problems seemed to need arrays, or actual string manipulation or 2D arrays, which are worse to do in Emily. Eventually I noticed Problem D.

Problem D: Ominus Omino - (The one with n-ominos)


When I read this problem, it seemed that the small input can be solved with a bunch of conditionals. And the results are just one of two strings. Conditionals are good news because at least they can be implemented in Emily. And we can print fixed strings. I would only need to use my text editor's regexes to turn input files into code that calls my Emily solution.

To solve this problem (The small version) you can just try all variations of R and C, and just try by yourself, is it possible to pick an n-omino that stops the other player from winning?

This is how my notebook looked after this:

The rest was just implementing everything on Emily. It was HARD. So many conditions. The interesting thing about Emily is everything is an unary function. And I mean EVERYTHING. This includes objects and numbers. Unfortunately, I couldn't think of a good way to think advantage of this in this problem.

\version 0.1

# Hi, I am using a language called Emily, it is in version 0.1 :/


min = ^a ^b (
    (a < b) ? a : b
max = ^a ^b (
    (a > b) ? a : b

case4 = ^R ^C (
    ( (max R C) == 4 && ( (min R C) >= 3 ) ) ? ALWAYSAWAY : CANMAKELOSE

case3 = ^R ^C (
    a = max R C
    b = min R C
    maxIs4 = ( (b == 3) ? ALWAYSAWAY : CANMAKELOSE )
    maxIs3 = ( ((b == 3) || (b == 2) ) ? ALWAYSAWAY : CANMAKELOSE )
    (a == 4) ? maxIs4 : (  (a == 3) ? maxIs3 : CANMAKELOSE )

even = ^X (
    ( (X == 0) || (X == 2) || (X == 4) )

case2 = ^R ^C (
    ( (even R) || (even C) ) ? ALWAYSAWAY : CANMAKELOSE

# woops, here was my mistake
case1 = ^R ^C (

mode = ^X(
   ( X==1? case1: X==2? case2: X==3? case3: X==4? case4: null ) 

solution = ^X ^R ^C (
    ( mode(X) ) R C

# Examples
println: solution 2 2 2
println: solution 2 1 3
println: solution 4 4 1
println: solution 3 2 3

I couldn't help but get carried away with the functional programming here. Case4 is a function that solves the case for tetraominoes, Case3 for tetraominoes, etc. mode is a function that picks which function to use according to X. I wanted this to just be an array, but apparently that's currently a bit difficult to do.

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