Saturday, November 16, 2013

Bragging about incoming Greed features part 2

Last time I mentioned that Greed Topcoder arena plugin is getting a 2.0 version that has plenty of nice features. Between that last post and today, many things happened. The first is that Greed 2.0 is now officially in beta state. So you can now get the jar in the releases page. If you used Greed 1.5, the configuration has really changed, it might actually be more productive to start configuration all over from the beginning and try to reuse your templates if they were too complicated. (There is only one breaking change in the template format, the ;zeroVal was changed with ;zerovalue, but the configuration file has really changed).

Also important: I committed a couple of cool things that will also be part of the new version. These changes are not in the beta jar, so you might have to compile the git branch yourself if you want to try them now. If you can wait, that's better.

Modulo detection

Counting problems in algo contests tend to ask you for the result modulo 1000000007, or modulo 1000000009 or some other large prime. This is because everyone hates bignums. Anyway, it does add a bit of an annoyance when solving these problems, you have to paste the number in your code, preferably as a constant. In TopCoder, they have the bad habit of using the absurd format that uses commas as separators , so the constant appears in the statement as 1,000,000,007. So you actually have to remove the commas. This is if you actually think of using copy paste, maybe you don't and just type the number manually, possibly typing the wrong number (like using 1000000009 instead of 1000000007 or missing a zero).

We deserve better. Now that greed has access to the problem statement, it occurred to me that it could totally try to detect this modulo. It looks for the phrase ":modulo (some number)" and then saves the number in a convenient spot. If there are multiple of them, it saves the last one that is mentioned, because that tends to be one of the last phrases in the statement. It probably won't work all the time, but most of the time it shall be of some help.

My template looks like this:

${<if Problem.Description.Modulo}
    static const int MOD = ${Problem.Description.Modulo}; 

The result is:

    static const int MOD = 1000000007;

Or whatever number is parsed. This constant is only added if the Modulo was detected. You know, automatically.

The colorful templates with generic tester

I added tweaked versions of my current templates so that it is easy to use them in greed out of the box after just tweaking two configuration lines.

More info

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