@PeterTaylor I think another interesting challenge would be to generate tuples with uniform randomness, where tuples with repeated elements should have the same probabilities as those with unique elements.
I'm not even sure how I'd do that, short of generating all of them and picking a random one.
Shuffle an Array
code-golfarray-manipulationrandompermutations
The task is pretty simple: given an array of integers, shuffle it. There are a few rules though:
Every possible permutation must be returned with the same probability (so the shuffle should have a uniform distribution).
You must n...
@PeterTaylor Hm, there are a few other randomness challenge ideas that sound conceptually simple but are actually a bit tricky. I'm thinking I could turn this into a series of challenges. Random permutation. Random tuples or subsets. Random (integer) partition.
@PeterTaylor okay, I think I've got ~9 ideas to potentially make a golf course from this. would you mind helping me sift through them see if some of them may have been done/have trivial shortcuts/turn out to be equivalent? (doesn't have to be today)
@randomra you're good with J, right? is there an equivalent to & and @ (tracking) for hooks and forks? basically, I'd like to write (f g) with monadic g and dyadic f, such that it automatically applies to each element in a list, without having to use "0
Find your Local Timezone
kolmogorov-complexity code-golf
(Challenge "inspired" by the now-closed Rise and Shine!.)
Summary
Input: Two integers, the latitude (-66 ≤ y ≤ 66), and the longitude (-179 ≤ x ≤ 179).
Output: The timezone offset in the hours from UTC at the given position, on 2015 Fe...
@MartinBüttner I'm not actually sure exactly what you mean by that. But it's worth bearing in mind that random combinatorial object is closely related to counting the combinatorial objects.
I'm sure I have done shuffling in GS by randomly selecting one from the list, but that's not as easy to find as the now standard technique of shuffling by {;large_number rand}$, which I learnt from someone else. Possibly Ilmari.
Counting, not enumerating (in the sense of iterating).
the idea is you're given a pool of numbers, say 1 1 2 2 2 3 4 5 5 6, and you're to generate a random 2-tuple (say) with uniform distribution, such that (1, 1), (1, 2), (2, 1) and (2, 2) all have the same probability
@randomra basically... I've got a list of boxes, each of which contains a list of numbers (of different length)... I want to unbox each of those boxes, and perform an operation on the contained lists without all of them being expanded to fit into a single table first
Coming back to the point about the relationship between random selection and counting, one of your ideas was random partition. With the right recurrence the code to count can be easily adapted to select one at random. (It wouldn't be at all easy to adapt an analytic-combinatoric computation).
@randomra well, f also uses x ... actually it's more like f(x,g(h(x))) where h produces the list of boxes from x
@PeterTaylor how would you ensure the selection is uniform, though? surely you can't know the different sizes of the recursion branches up front to bias them correctly? would you run the recursion twice, once bottom-up to find the biases and then top down to determine a partition?
That's one way. Another is to make it so that instead of returning a count it returns a count and a partition; then when it combines them by adding the numbers it can also do a weighted random selection between the partitions.
Elevator Control [WIP]
The controller is still a WIP, but I have a decent idea of how it'll work.
You have been hired as a Vertical Integration Specialist (programmer) at Ascension Incorporated to write advanced elevator controller software. (backstory wip)
Elevators are Cool
The current setu...
Shuffle an Array
code-golfarray-manipulationrandompermutations
The task is pretty simple: given an array of integers, shuffle it. There are a few rules though:
Every possible permutation must be returned with the same probability (so the shuffle should have a uniform distribution).
You must n...
Find your Local Timezone
kolmogorov-complexity code-golf
(Challenge "inspired" by the now-closed Rise and Shine!.)
Summary
Input: Two integers, the latitude (-66 ≤ y ≤ 66), and the longitude (-179 ≤ x ≤ 179).
Output: The timezone offset in the hours from UTC at the given position, on 2015 Fe...
Elevator Control [WIP]
The controller is still a WIP, but I have a decent idea of how it'll work.
You have been hired as a Vertical Integration Specialist (programmer) at Ascension Incorporated to write advanced elevator controller software. (backstory wip)
Elevators are Cool
The current setu...
