12:00 PM
Challenge type idea: Hand crafting a QR code, with certain conditions.

0

Stackable sequences You deal cards labeled 0 to 9 from a deck. When you deal a 0, you place it to start a new stack. When you deal any other card, you stack it atop a card that's exactly one lower in value, covering it. That way, each stack starts at 0 and counts up by 1. If you can't place the ...

12:17 PM
@zyabin101 Has been done I think

@Bas I mean, make the QR code with the smallest side length.

@zyabin101 Ah okay, cool

> A lock is a private/public system where a physical public key is used to access the internal private mechanism(tumbler). When a user inserts a copy of the public key, they can gain access to the door and can modify it's internal states(like unlocking, and locking it).

12:35 PM
speaking of locks
there is a cool analogue of RSA that allows you to securely transfer the contents of a box from one person to another with just padlocks, without having to give away your key
alice puts the thing to transfer in a box, and locks the box with her padlock
she sends the box to bob, who also puts his padlock on the box (so now it's doubly locked), and sends the box back
alice removes her padlock, leaving just bob's padlock, and sends the box again
now bob can remove his padlock, and can open the box
@QPaysTaxes asymmetric*

^^ I got asked that by my maths teacher many years ago when I was bored in class. The only difference was that the box had a teddy bear and the postman was really evil

@Sp3000 we also assume that the postman does not possess an angle grinder :P

Yeah, I didn't get it at the time. I said "use a num-lock" to which she responded "if Bob has the patience the crack that, then so does the evil postman"

> will hunt down and arrest kill the person responsible.
ftfy

> will try to hunt down but will never find the NSA operative
here's another plan
you ship 100 boxes
one of which contains the teddy bear

12:44 PM
@orlp That's even more shipping charges

@QPaysTaxes How do you tell Bob that the strip of paper is actually significant without the postman knowing?

the others contain anthrax that is immediately spread into the air when the box is opened

@orlp 2 x heavy duty padlocks is way cheaper

@orlp Oh, that's easy. You just get a lineup of 100 prisoners that are tired of thinking about a light bulb ...

I'll stick with the tripled shipping charge, thanks

12:46 PM
I like your unorthodox ways of thinking

> you ship 100 boxes
@Sp3000 ^ Compared to x100 shipping charges, it's a lot cheaper

alternatively
we can do a key exchange
we do the triple shipping charge thing once
but we're not shipping a teddy bear
we're shipping a duplicate key for a padlock
so that both alice and bob have the key
this is a one-time setup cost of 3 shipping charges
but sending the bear now only costs 1 shipping charge

@orlp *Multiple duplicate keys

@MarsUltor why?

Well, in the real world analogy, it's a lot cheaper (for future teddy bears)

12:49 PM
If you do want to send a lot of boxes though, you can send 1000 num-locked boxes, each of which just has a number and a long passcode inside. Bob picks one, cracks it, then tells Alice "I cracked number #n". Alice then sends the real box, with a mega-numlock where the code is the passcode Bob chose.

But of someone happens upon them, then it's not good

@Sp3000 If the postman is evil enough, he will memorize the passcodes in all 1000 boxes

Hmm, guess we need more boxes then.

@Sp3000 Bob should instead pick 2 boxes and concatenate the passcodes

@Downgoat Preinitialise `ಠ_ಠ` to `ಠ_ಠ` :P
Golfier. :P

12:51 PM
2 boxes actually doesn't help all that much

@Sp3000 No actually you're right

You could probably skip the mail thing and just have Alice take a plane and hand it to him. Cheaper that way.

Actual solution: avoid this and use RSA

@MarsUltor ಠ_ಠ

You can't RSA a teddy bear :(
6

12:52 PM
@Geobits Unless you can hide in the luggage compartment, that doesn't stop the postman being the pilot

Actual actual solution: Pay your neighbour kid 20 cents to deliver it to Bob

Saves almost 100% shipping charges, reduces authorities after you by almost 100%

@Geobits You can RSA a teddy bear. :-)

@zyabin101 3d printers are a thing nowadays

@Geobits You can heavy-duty padlock a heavy-duty box containing a teddy bear

12:53 PM
@Sp3000 Ok, but what postman that could also turn out to be a pilot couldn't get his hands on a \$10 pair of bolt-cutters?

Why doesn't Alice just invite Bob over for tea and give him the bear in person? I mean, they're obviously good enough friends that they're exchanging teddy bears, maybe it's time they take the relationship to the next level.

@TimmyD Maybe they're pen pals?

@TimmyD And while they're at it, make some use for the teddy bear as well (if you know what I mean)

@Geobits I dunno, this is the same world where Alice needs to send a box to Bob for some unknown reason. We make this up as we go, right?

Why is this postman such an ass anyway?
Did a teddy bear hurt him in the past?

12:55 PM
@Geobits Because Bob stole his ex-girlfriend (Alice) obviously

@zyabin101 Alice takes a photograph of the teddy bear with a link to it on an e-Store and a gift card for that store steganographed over it, then RSA's the result and sends to Bob.

@Bas I kinda always knew she'd end up his ex-girlfriend.
@zyabin101 So then Bob orders it and the postman steals it enroute. Genius :)

> Oak: I don't know who you are, but I will find you, and I will tell you that now is not the time for that.

@Geobits The postman's name is Eve.
Right. ( ͡° ͜ʖ ͡°)

@Geobits Well, but if the postman is looking for a package from Alice, this just may work.

1:03 PM
Any smart postman would be monitoring all of Bob's mail, but I suppose you could fool a dumb one this way.

Well, meaning is the postman intercepting Alice's mail going outbound, or Bob's mail coming inbound.

Then again, there are probably easier ways if that's the case. Just put a false return address on it for instance.

guys
I have a confession to make
I secretly have a superpower

Is it being able to add 1 to any integer?

Oh, is it the power to fill things up?

1:04 PM
0

Golf K-means K-means is a standard unsupervised clustering algorithm, which, given a set of "points" and a number of clusters K, will assign each "point" to one of K clusters. Pseudo-Code of K-means Note that there are many variants of K-means. You have to implement the algorithm I am describi...

Cuz that's a great super power. Car run out of gas? Fill it up. Bank account empty? Fill it up. Fighting a bad guy? Fill up their bladder.

Huh, I coulda sworn we already had a k-means golf, but I can't find it.

My super power is... the gift of hindsight.

Oh, so like Captain Hindsight?

I knew he was gonna say that.

1:07 PM
@orlp Let me guess, in hindsight you should've picked another superpower
@Geobits Wow, you're gifted as well

That's what they tell me.

1:19 PM
Rip great conversation about teddy bears, evil postmen, RSA and other nonsense

@Bas Live forever great conversation about teddy bears, evil postmen, RSA and other nonsense!
Book marking conversation.

@zyabin101 How?

@Bas I'll use the room menu!
How should the great conversation about teddy bears, evil postmen, RSA and other nonsense be called?

Ah cool I see

@orlp ^^

1:22 PM
Why not exactly that? Lol

@Bas Done.

### About teddy bears, evil postmen, RSA and other nonsense

47 mins ago, 31 minutes total – 99 messages, 9 users, 1 star

Bookmarked 11 secs ago by zyabin101

@zyabin101 Sweet

@zyabin101 no, that repo contains the bot password and anyone can use him.

@EᴀsᴛᴇʀʟʏIʀᴋ No, that repo contains the bot password and that's bad. Hackers can see the bot password on GitHub and log into the bot's account to spam the room. That's why the password must be sanitised.
It's even better to use the Slack API for Bot Users instead.
But idk how to use it with Python ¯\_(ಠ͜ ಠ)_/¯

Slack Api is garbage.
@CᴏɴᴏʀO'Bʀɪᴇɴ according to my parents, even if you are not a stalker you are still a bad influence and thus so is code golf. My time here will be reduced for the next week.
Bai!

1:34 PM
@EᴀsᴛᴇʀʟʏIʀᴋ wai ;_;
@EᴀsᴛᴇʀʟʏIʀᴋ BAI

Becaus I spend too much time in the blogosphere

b-b-but it powers almost every bot on Slack.
Including Hubot! Wai you indirectly dislike Hubot? ;_;

Yeah.

@EᴀsᴛᴇʀʟʏIʀᴋ And what?

@Mego Do you know which IRC daemons support svsnick?

1:46 PM
@zyabin101 ?

@EᴀsᴛᴇʀʟʏIʀᴋ You said yeah, and what?

Slack api is too complicated. Give everbody free source code access. :P

@EᴀsᴛᴇʀʟʏIʀᴋ ಠ_ಠ It isn't.

Looks like you just open a websocket and send appropriate bits of JSON

Has too many api keys and permissions.
Well, bai!

1:54 PM
BAI

Do we have a challenge to add two numbers?
or anything duplicate of it?

@KennyLau ...joke, right?

@KennyLau I sure as hell hope so

@quartata Just asking if we have such a challenge.

@EᴀsᴛᴇʀʟʏIʀᴋ github.com/os/slacker

1:56 PM
If not, you could make one and get downvoted to oblivion :p
There's trivial, and there's adding 2 numbers trivial

Yeah, we've probably got that covered somewhere in this selection of 369 challenges ...

@TimmyD Can't find one.

Well, if you can make it interesting, with enough of a challenge to make it more difficult than a one-byte answer (which is what it would be in many esolangs), go ahead and Sandbox it up.

Challenge idea: make a program which computes the string with the smallest possible MD5 hash.
The string may only include printable ASCII, and it must finish in 30 seconds.

@KennyLau Here are three PowerShell solutions, all of them 17 bytes in length oddly enough
```param(\$a,\$b)\$a+\$b
\$args[0]+\$args[1]
\$args-join'+'|iex```

2:03 PM
I know you are trying to say that computing the string with the smallest possible MD5 hash in 30 seconds is impossible. Ikr.
But you have to try to get the smallest hash.

@zyabin101 I think that was directed at the "add two numbers" challenge

@TimmyD We already have this :(
39

I want to try a new type of regex golf challenge, which asks you to solve nontrivial computational tasks with nothing but regex substitution. To make this more possible and less of a chore, you will be allowed to apply several substitutions, one after the other. The Challenge We'll start simple...

@Bas Ah.
@Bas That wasn't.

@TimmyD Is the `|` a pipe like in bash?
Powershell actually looks like it might be fun to golf in

@quartata Kinda. It's an intrinsic part of the language itself, rather than a separation between components like in other shells.
The key point to remember is that PowerShell is an object pipeline, not a string pipeline like other shells. Passing things from one command or value to another via the pipe passes it as an object, so methods and the like can be preserved and manipulated.
For a really simplistic example, here's an Exchange-specific command
`Get-AddressList | Update-AddressList`
The first command will return a collection (it can be thought of as an array, though it's not really) of all address lists in the environment. The second command will be able to implicitly parse the `.Identity` parameter of the input object(s) and use that for execution.

2:17 PM
0

this is the brief I have to do: Its for an athletics long jump contest. The program will 1. prompt the user for the names of competitors, then 2. for each competitor, ask for the distances that they jumped, then 3. print a table of competitors and their best jumps, and then finally, 4. print the ...

`Thanks @NewM..... nothing`

I haven't gotten much feedback on my meta post:
6

We've got some pretty great challenges here. However, after a month or so, challenges get little to no activity. Since we aren't a Q&A site, we rarely get traffic via searches. I would love it if we could introduce users to high quality questions that they may not have found on their own. I b...

If this does happen, it needs quite a bit of community participation, so I'd like to know if it is interesting (aka, would you participate?)

> In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move.
@NathanMerrill I think we should feature no more than one challenge per author in the tour, to promote variety

@orlp I agree that variety is important, but I'm not sure if that restriction really promotes variety. We have quite a few challenges from Helka Homba that are quite different from each other
(for example)

Otherwise most challenges would be Calvin's Hobbies'… whose challenges are much better than Helka Homba

2:26 PM
I didn't mean variety in terms of challenges
@Fatalize agreed, calvin is much better than helka

@NathanMerrill I'm with orlp on the promote-author-variety aspect. I also think it would be better if we narrowed the scope of the tour. Something like a tour of string manipulation challenges ... a tour of sequence and subsequence challenges ... etc.

10

It is well known, in the field of Mathematics studying infinity, that the Cartesian product of any finite amount of countable sets is also countable. Your task is to write two programs to implement this, one to map from list to integer, one to map from integer to list. Your function must be bij...

@TimmyD On my post, you'll see I've considered doing themes for future challenges, but this first one is unthemed.

I have an interesting solution to this that I can't seem to efficiently code
list -> number
add 1 to each element in the list, convert to binary, and strip the leading 1

I'm not sure why we need author-variety. I mean, even if Calvin has the top 25 challenges (which I don't think is the case), what's the problem?

2:29 PM
@NathanMerrill Yeah, I see you added that a few minutes ago. I was going off of memory from last night's read before you edited it.

@TimmyD :)

join by 2 to get a ternary number

So, I'm trying to run answers to this question on a test case, and see which number is the smallest for the test case.
The case is [0, 1, 2, 3, 0]
```78977 exactly maps [0, 1, 2, 3, 0] to 652190.
78989 exactly maps [0, 1, 2, 3, 0] to 1681.
652190 / 1681 = 387.97739440809045

78989 is winning.```
Wow, that's a large ratio.
Meanwhile, idk what to write for zyabinVI :/

2

An indian legend tells the story of the alleged inventor of the chess game, who impressed so much the emperor of India with his game that he would get rewarded with anything asked. The man said he wanted to be paid in rice. He wanted a grain of rice for the first square of the chessboard, two fo...

@zyabin101 what even is ZyabinVI

2:42 PM
My experimenting organization. :P
Currently in all of the definition, commitment and beta phases.
Definition is for, we don't have people in the org. Only me. Also, there is one failed invite.
Commitment is for, everyone can contribute something to be invited to the org.

yeah but
what's the point of it
the goal

@Fatalize Experimenting. :P

experimenting what?

@Fatalize Uhh, just experimenting.

Hi @NewMainPosts

2:47 PM
Hi @NewSandboxedPosts

why VI and not V or VII?

@orlp wish I had seen that challenge before Dennis did. I have a matlab program around here somewhere that works exactly the way his works and could have been easily ported to MATL

CSS or HTML should have the ability to put some "flag" that disables the default stylesheet on browsers

oh well

@NathanMerrill @important?

2:48 PM
no
no way

@Fatalize I chose whatever I wanted. :)

0

Determine If a Challenge is Worth Answering I am a very casual code golfer, and don't often see posts until the show up in the "Hot Network Questions" sidebar over on StackOverflow. Usually, I'm late to the game, and since the only language I know is Python, there is little point in me answerin...

while there are reset stylesheets, they go out of date, and they require sending additional data for the website
simply having some sort of flag that says "Hey, don't apply any default styling to this page, only mine" would be awesome

@NathanMerrill That would also break many customized settings required for the blind or other hard-of-seeing, or for other things like screen readers or aggregators.

. ͜ .

2:53 PM
@TimmyD maybe? It's not like users wouldn't be able to override it, and browsers wouldn't have to follow it in cases like that

The Conway base 13 function is a function created by British mathematician John H. Conway as a counterexample to the converse of the intermediate value theorem. In other words, even though Conway's function f is not continuous, if f(a) < f(b) and an arbitrary value x is chosen such that f(a) < x < f(b), a point c lying between a and b can always be found such that f(c) = x. In fact, this function is even stronger than this: it takes on every real value in each interval on the real line. == The Conway base 13 function == === Purpose === The Conway base 13 function was created as part of a "produce...

@NathanMerrill Mmm, maybe I'm not understanding, then, because if the flag is optional, isn't that the same behavior that's currently present?

> In fact, this function is even stronger than this: it takes on every real value in each interval on the real line.

how do I reverse the order of arguments to a dyad in Jelly?
e.g. in the current link I have the current value a, and I want to calculate b^a for some argument b, but `*` calculates a^b

3:06 PM
@TimmyD its similar to clear stylesheets. Right now, if I don't want all <a> tags to be underlined, I need to add a stylesheet that overrides the default. However, browsers don't have to use stylesheets. If I'm reading impaired, I may simply never apply stylesheets on a webpage.

now working on implementing `encoding.rb`.

but the flag that says "don't apply default styling" could similarly be ignored if the user/browser wanted to. But right now, no browser supports such a flag, AFAIK

@ArtOfCode ¯\_(ツ)_/¯

Ah, I see what you mean, now.

Ok, ruby question.
So I have an array `a`. Let's say I want to run `eval` on each element. The conventional way would be `a.map{|x|eval x}`, but is there a way I can pass the reference to eval? Like how I can do `a.map(&proc)`?

3:14 PM
PowerShell `\$a|%{([REF]\$_)|iex}`
I know that doesn't really help, I just wanted to contribute
:D
(whoops, forgot the `[REF]` tag)

A bit of shameless self-promotion. While trying to figure out test cases for the negative font challenge, I've come across an interesting combinatorics problem:
1

I'm looking for a set \$S\$ of (ordered) lists of \$n\$ numbers such that: Each number appears at least once as the first numbers. Each number appears at least once as the last numbers. Each possible ordered pair of adjacent numbers should appear at least once. Let's say I'm looking at the number...

@Dennis is there really not an atom for the exclusive range [0, n)?
and if `’S` is really the way to go, why didn't you make the exclusive range the default?

Indexing in 1-based in Jelly. Having a built-in for [1, n] makes more sense than having one for [0, n) imho.

oh
why did you choose 1-based indexing?

Because I wanted all indices to be truthy. Find returning 0 for not found has been useful more than once.

3:21 PM
Hrm, doesn't seem worth it IMO

@MartinBüttner I'm unsure why you have the "first index" and "last index" restrictions

can always check for `find == -1`

are they arbitrary, or is there something I'm missing?

1

Print the Nth non-palindromic number A palindromic number (in case you don't know) is a number which reads the same backwards and forwards (example, 11). The first 15 non-palindromic numbers are: 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23, 24, 25, 26. They can be found at the OEIS here. I co...

0

This was inspired by a Minecraft mini-game. The rules are pretty simple: you run and jump around, and every block you step on disappears once you've stepped on it. The goal is to be the last one left. Your bot should be a complete program. It should accept input as a command line argument. The i...

@NathanMerrill they don't seem to affect the problem, but I'm not sure how to prove it.
or maybe I am
due to the Hamiltonian cover equivalence

3:23 PM
@orlp There really aren't any downsides to 1-based indexing I'm aware of. It's still modular, so 0 gives the last element, -1 the second to last, etc.

@NathanMerrill anyway, the reason I have them is that in the underlying problem the first and last number form a unique "pair" with the start and end of the list.

@Dennis You could always pull a Mathematica and make `1` the first element, `-1` the last element (and 0 a super-special-surprise)

For an editor named Brackets, you don't seem to handle indenting them very well. ಠ_ಠ

? I didn't see that. For example, in your n=7 example, your 11234567 example makes the pair 7,1 (which exist in 66524371)

3:25 PM
@Sp3000 Map 0 to HCF?

So the "element" at index 0 is the type?

hmmm, this seems related to the De Bruijn

@NathanMerrill the list is not cyclic

@MartinBüttner then what do you mean by this?

3:28 PM
introduce a "start of list marker" (e.g. `^`) and an "end of list marker" (e.g. `\$`). now look for all possible pairs with those included (where having `^` second, `\$` first, or `(^,\$)` are not considered possible)

> the challenge was to produce a simple-to-understand function which takes on every real value in every interval
Amazingly, the utterly crazy function is actually simple to understand
That's what I wasn't expecting...

hahaha, indeed :P

@Dennis Can you please pull 05AB1E?

3:33 PM
Thanks :)

@MartinBüttner are you concatenating the numbers?
or is that just to condense the notation

I accidentally deleted most of the content of my Desktop! ;_;

@orlp condensed notation
okay, test cases done, does this look ready for posting?
5

Between the Lines code-golfgraphical-outputnumber While doodling around on square-ruled paper the other day, I came up with the above negative-space font for digits. In case you haven't spotted it yet, the spaces between the above shapes yield the golden ratio 1.618033988749. In this challeng...

maybe refer to that?
rather than specifying image I/O yourself

the post is less than a day old, I'd rather specify it myself than refer to a consensus that is still in the process of forming ;)

3:37 PM
The voting culture on graphicdesign.SE is worse than on SO. And that's not easy.

(also even for normal I/O I always specify it myself, because I don't want people to have to go looking at the meta post)

I just wrote a programming version of the Navy Seals copypasta.

@MartinBüttner Looks good to me

hi all

3:41 PM
```1221
2332
3113```
@MartinBüttner ^

I was reading this answer on Quora that debunks myths about Chile, one of which is that "Chile is very narrow". The answerer basically said "No, it's not that narrow; it takes three hours to go from one side to the other, and it's like that for a few European countries too." ...... As an American, that is very narrow. :P

@orlp see the last bullet point

@MartinBüttner wait, I didn't see the constraint that got dropped
what constraint?

that the lists are permutations with the first element repeated
clarified

ah I see now

3:46 PM
@El'endiaStarman Ha, yea. It takes me three hours to get halfway through my state.

typography tag, yes/no?

Hmm. It could apply to a few others I think.

there are 12 challenges with the tag

algo/coding question. If I give you 9 letters and ask you to produce the longest word in a dictionary that can be made from a subset,how long does that take?

Oh, I thought you were asking if you should create it.

3:49 PM
@Lembik 7 minutes

@Lembik With or without repeating letters?

@Geobits no I created it a while ago, just wondering if it's a bit of a stretch to apply it here. :)

@MartinBüttner :) I meant is there linear time algo
@Sp3000 with

@MartinBüttner The challenge can be summarised as "output a font" so it seems to fit

3:50 PM
okay, posted :)

@MartinBüttner I'll count down.
Three...
Two...
One...
Challenge!

or not

Nice try, @zyabin101. ಠ_ಠ

@Lembik By "made from a subset", do you mean you want words that use only that 9 letters, or that you're picking k <= 9 of the 9 letters and you want words using only those k letters?

@Sp3000 words that use only that 9 letters but you don't have to use all of them
you need to use as many as possilbe

3:52 PM
So... is length of word the priority or number of different letters used?

@Sp3000 length of the word
hmm..I suppose 9! isn't that large :)

Then can't you pass through each word, keeping track of which of the 9 letters have been seen as you go, breaking out if you see an unrecognised letter. If you make it to the end then the word uses only those 9 letters, at which point you check if it's longer than the current record?
Not sure if I'm misunderstanding

3

While doodling around on square-ruled paper the other day, I came up with the above negative-space font for digits. In case you haven't spotted it yet, the spaces between the above shapes yield the golden ratio 1.618033988749. In this challenge, your task is to take a number as input and render...

@Geobits I was thinking that too - every state I've lived in is longer than three hours, though not all are wider (top to bottom) than three hours. Still, the narrowest one is like 2.5 hours, so...