The Nineteenth Byte

9:41 AM

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Do the 26 richest billionaires own as much wealth as the poorest 3.8 billion people? code-golfnumberinteger Introduction: I just read this post with the same title when I came across it in the HNQ. In this question it is being discussed if the claim of president-candidate Bernie Sanders, who c...

12:44 PM

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H interpreter H is a relatively simple language that does not implement advanced features. Create an interpreter for H. The winning criterion for this challenge is code-challenge. Here is everything in the H command reference just for reference purposes: Def The def command is used to define...

3:47 PM

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Enable 2-char Jsfuck Provide a shortest code that makes JavaScript able to do everything JavaScript is supposed to do, with only [ and ]. You can choose your environment(FF/node/etc). Answering in 6-char JsFuck or something similar is welcomed.

5:29 PM

I recently discovered toolz, a Python library for functional programming, and I have fallen in love with it

github.com/pytoolz/toolz

Oliver

5:51 PM

Any mod feel like updating the site name mentioned here?

Adám

6:07 PM

@Mego @DJMcMayhem @Dennis ^

Should I say "Code Golf & Coding Challenges", or just "Code Golf"? I prefer the second

Oliver

I like Code Golf

> Code Golf

but be sure to put it in italics

oh, and there's one at the bottom too!

status-completed

btw, the italics are important in that page because PPCG might be somebody's first interaction with SE, but they might already know what "code golf" means, and then they could be like "um... wut" otherwise

Veskah

6:15 PM

Needs to be in 72 pt. Impact Bold

Gotta be subtle, ya know?

btw, it might be time to get this off the Featured list

I like S͟U͟B͟T͟L͟E͟T͟Y͟ too

inb4 "w?h?a?t? ?a?r?e? ?y?o?u? ?s?a?y?i?n?g? ?t?h?e?r?e???" :D

Oliver

If anyone wants a better visual of the new header, you can go here: https://cdn.sstatic.net/Sites/codegolfmeta/img/header-background-image.svg?v=7b61cc011d06

and run:
var allElements = document.getElementsByTagName("*");
for(var i = 0; i < allElements.length; i++) {
var element = allElements[i];

if(element.getAttribute("fill")) {
element.setAttribute("fill", "black");
}
}

2

AdmBorkBork

@DJMcMayhem Subtle. Like the b.

6:29 PM

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Implement ave This is one part of a multi-part series inspired by various built-ins in R. Credit goes to digEmAll for suggesting this one. ave calculates particular grouped values of a list. For example, we would group x in the following way based on the criteria given in f: x = [2, 1, 3, 5...

It's funny, the word "subtle" looks correct to me, but no matter how many times I double check the word "subtlety", it looks like it's spelled wrong to me.

Veskah

Subtle Tea

6:52 PM

If I have a directed graph generated from permutations and it is generated as integers from 1 to "n". I have the original sequence and I need to check if that sequence can be constructed from the graph. for example lets say the permutation sequence is [4,1,5,2,6,3] and our adjacency matrix for our graph is {1:[5],2:[6],5:[2],4:[1],6:[3]} Would the Hamiltonian path in the graph be considered the original order of the sequence assuming we have the correct starting vertex?

If I understand what you're saying, then yes

I'm kind of confused about your specification for the adjacency matrix though

thank you!! I thought I might have been losing my mind there for a second

I think it would be easier to understand if you put it in order, like {4:1, 1:5, 5:2, 2:6, 6:3}

@ThePlasmaRailgun well it's a directed graph the sequences are like this [[5,2,6,3],[4,1,5,2]] but I interperate it as this {1:[5],2:[6],5:[2],4:[1],6:[3]}

Yes, but that's the exact same adjacency matrix, just slightly shuffled so it's easier to just look through and verify it follows a hamiltonian path equivalent to your permutation

6:59 PM

@ThePlasmaRailgun good point that would have made it a lot easier

@ThePlasmaRailgun are there any nice theorems for a Hamilton path

Also, you might want to look at Rook generators, which are polynomials generating the number of possible matrices where every nonzero value is a 1, and every row and column contains only a single 1, no more, no less.

That ends up being a problem of how many possible permutations there are

Ignoring rotations and mirrorings

Which is an interesting little twist that can end up being useful

nice! will do that

If you're interested specifically in permutations where no element stays in it's original place, that's called a derangement problem, and there is also a formula for it, it ends up being equivalent to a similar "rook problem" where placing 1s in the diagonal is forbidden

derangement problem is this mostly used in encryption or decryption

It's used in a lot of things

IDK about encryption, I don't think it's in any major algorithms

Anytime when you want to reorder something so that the elements are not in original order, that's derangement

7:08 PM

sorry what I really meant what kind of problems is it mostly used toward solving

Oh

Here's wikipedia's example: Suppose that a professor gave a test to 4 students – A, B, C, and D – and wants to let them grade each other's tests. Of course, no student should grade his or her own test. How many ways could the professor hand the tests back to the students for grading, such that no student received his or her own test back?

It really ends up being used almost anywhere permutations are used, because it's just a slightly restricted permutation

interesting so distribution at scale

Random permutations are used pretty often in interleaving and deinterleaving, which are methods to make signals more robust

Interleaving is frequently used in digital communication and storage systems to improve the performance of forward error correcting codes. Many communication
channels are not memoryless: errors typically occur in bursts rather than independently. If the number of errors within a code word exceeds the error-correcting code's capability, it fails to recover the original code word. Interleaving ameliorates this problem by shuffling source symbols across several code words, thereby creating a more uniform distribution of errors.[12] Therefore, interleaving is widely used for burst error-correct…

@ThePlasmaRailgun thanks a lot that really did help! :)

No problem!

New Main Posts

7:29 PM

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Q: Write an interpreter for H

H is a text-based, weakly-typed language. Create an interpreter for H. The winning criterion for this challenge is described in popularity-contest. Here is everything in the H command reference; the command reference of H is very hard to navigate through, and some parts are missing. Please do ...

8:11 PM

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