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12:39 AM
A: Sandbox for Proposed Challenges

RGSBinary multiples A binary multiple of a positive integer n is a positive integer m such that m is written only with 0s and 1s in base 10. For example, 111111 is a binary multiple of 3. It is easy to show that a positive integer has infinitely many binary multiples. Your task Given a positive ...

12:55 AM
@JPeroutek You can just change it to whatever you like.
6 hours later…
6:46 AM
A: Sandbox for Proposed Challenges

CJ DennisI want to ask a combined popularity / objectively scored question. Something like: Take a string as input. Match the string to a famous painting such as "Mona Lisa" and render a cartoon version of it. 1 point per painting, 1 point per upvote. Voting closes on XX/YY/ZZZZ. I want to reward pe...

1 hour later…
8:16 AM
Q: ASCII Pizza (no pineapple)

RGSI like pizza! Task Given the radius of a pizza and a list of ingredients, create the corresponding ascii pizza! Example size 4 pizza with mozzarella cheese, olives and ham: ##### #@@@@M# #H@O@@@@# #M@@@H@@# #@OO@@@@# #@@H@@@@# #M@M@@@@# #O@@@H# ##### Input A positive integer r ...

@NewMainPosts JIT to see the question being posted. Unfortunately I can't answer it.
9:10 AM
hi all
could anyone guess if a NFA to DFA challenge might be popular ?
or is there anyone here in chat who might be interested?
9:31 AM
It can be done
@JohnDvorak Do you mean it's possible to do the conversion or it's possible that the challenge might be of interest?
The latter
oh cool
I was amazed to find how few programming languages have a library for this
as in.. I am not sure if any do except for GAP?
@JohnDvorak For code golf I wonder how many bytes Jelly can reduce geeksforgeeks.org/… to :)
I give 90% to it being a built-in in Mathematica, and 10% to it being added in the next version
... and that's pretty conservative
9:47 AM
10:09 AM
J has a builtin for state machine
no idea how to use it
10:19 AM
@FrownyFrog interesting
A: Sandbox for Proposed Challenges

Lyxalcode-bowlingn't code-golfstring If you place the suffix n't on any given word, it instantly means the opposite of the intended usage of the word. If you place the word not before any given word, it instantly negates the next word. Therefore, today's challenge is about turning words in the for...

Do y'all have any general feedback I could apply?
10:53 AM
given 4 line segments, what is the maximum number of possible intersection points?
11:25 AM
arbitrarily many
11:38 AM
6 I think
Not arbitrarily many. Infinitely many.
these are straight lines
I am not sure how you get more than 6
Same answer for straight lines and for line segments
are we agreed the answer is 6?
11:46 AM
how do you get more than 6?
i.e. 7
You can't get 7, but you can get infinitely many
oh I didn't say they were distinct you mean?
distinct isn't sufficient. You want non-collinearity.
given 4 non-colinear line segments, what is the maximum number of possible pairwise intersection points?
You also want to specify pairwise intersections, otherwise the answer is 1.
11:48 AM
actually..why is it 1?
Otherwise the question is how many points are incident to all of the lines rather than at least two
line segments; same answer
I am not sure I agree with the last point of pedantry
but I did with the previous ones :)
Intersection of multiple sets is defined as the intersection of the first set and the intersection of the remaining sets.
Pairwise intersection is a very different operation, more computationally expensive
Ordinary intersection of convex sets is convex, for one. Pairwise intersection doesn't.
is the answer just n choose 2?
It gets even more pedantic - intersections of finitely many elements behave much like binary intersections, intersections of countably many elements lose some properties (intersection of finitely many open balls is open, but not necessarily so of countably many), intersections of uncountably many elements lose even more...
2 hours later…
1:38 PM
@Anush pedantic++: you're all assuming euclidean geometry :)
Q: Find the number of edge in a graph

Alban DELPECHIn graph theory, you can describe a graph using a letter and its number of vertices. For example, the complete graph with 5 vertices is denoted by K5 There are many identifiers for many family of graph. Here is a non-exhaustive list : S : Star graph C : Cycle graph F : Friendship graph W : Whe...

2:21 PM
Q: String permutations

NohlPrint the largest number of strings, which are permutations of each other. If there is no permutations (for example, only one string was transmitted or the strings contain unique characters), print one of the strings. If no strings were passed, do not output anything. The output is always accompa...

@ngn False. I'm not assuming any of the five postulates, in fact! The only thing I assume is that any pair of distinct points has a unique line passing through it. And you pretty much need that assumption to do geometry.
@JohnDvorak how many meridians pass through the north and south pole?
If you want to do geometry on a sphere, you identify the antipodes
OK... CMC: identify the class of spaces in which you can do geometry (almost every pair of distinct points has a unique geodesic incident to both) yet fail the axiom that every such pair does.
@JohnDvorak the alternatives to euclidean are spherical (aka elliptic) and hyperbolic
False. Elliptic geometry = spherical geometry modulo antipodes
However spherical geometry is the natural double cover of elliptical geometry
OK... even easier CMC: identify any space not isomorphic to S^n where the above holds
2:37 PM
@JohnDvorak now i see what you mean. the north pole and south pole are the same "point"
Third CMC, medium difficulty: Identify any geometry where the set of point pairs that don't define unique lines isn't an equivalence class.
Q: Spam, egg, sausage and spam

ArnauldYou are given four integers: \$e,s,b\in\{0,1\}\$ and \$S\in \{0,1,2,4\}\$, where \$e,s,b,S\$ stand for egg, sausage, bacon and spam respectively. Your task is to figure out whether the corresponding ingredients match a valid entry in the following menu: [e]gg | [s]ausage | [b]acon | [S]pam ---...

1 hour later…
3:51 PM
@JohnDvorak "point pairs that don't define unique lines" - wouldn't the presence of such pairs contradict your assumption for doing geometry?
4:06 PM
Yes. But spherical geometry is called so even though it breaks the assumption.
5:03 PM
Q: Finding Radical Ideals

Don ThousandFinding radicals of arbitrary ideals in rings is hard! However, it's a doable task in polynomial rings, since they are Noetherian (all ideals are finitely generated) Background A ring is a set, paired with two binary operations + and * such that 0 is a additive identity, 1 is a multiplicative i...

5:34 PM
A: Sandbox for Proposed Challenges

wastlSimplify a directed graph code-golf graph-theory math Input A directed graph, in any convenient format. A valid format (and probably the most convenient) would be a list of edges. Simplification These two reductions are performed as often as possible. It does not suffice to apply one reducti...

Q: Game of Game of Life

Spitemasterking-of-the-hill javascript cellular-automata game-of-life game Game of Game of Life Conway's Game of Life is a 0-player game. But that's okay! We can make it a multi-player game. This game is played on the smallest square grid that will accommodate a 6x6 square for each player (12x12 for 2-...


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