# Posts by trichoplax

Given a chess board with some knights on it, say how many squares are neither attacked by a knight nor containing a knight. Input An 8 by 8 grid where each square is either a knight or empty T...

Given a sequence of letters, output only the vowels. Input A sequence of letters This may be a string or any ordered data structure of characters (provided it is consistent between inputs) Th...

Given a string, convert all of its letters using ROT13, and all of its digits using ROT5. This is sometimes referred to as ROT13.5. Input A sequence of printable ASCII characters (character cod...

This is a fixed output challenge. Output a textual representation of a chessboard hosting 8 queens, none of which are attacking each other. There are 92 ways of arranging them, 12 if rotations and...

Given a positive integer as input, indicate which base from 2 to 16 gives the most holes in the representation of the input in that base. The digits used are 0123456789ABCDEF. Note that these incl...

Given a sequence of letters, omit those with the highest or lowest pop count. Terminology The pop count or population count of a binary string is the number of 1s in it. For this challenge, the ...

Convert a matrix or grid of digits to its antitranspose. For a square matrix , this is its reflection in its antidiagonal. More generally, for a rectangular matrix, this is its reflection in its sk...

Given a sequence of lower case letters, sort them into order of height. Heights The heights of letters are dependent on font, so for this challenge the height order to be used is as defined below...

Given a word that can be rotated by 180 degrees (a half turn) about at least one of its 3 axes and continue to be composed of English alphabet letters, output one of its rotated forms. The 3 rotat...

Given a string of printable ASCII characters, convert them all to lowercase, except not just the letters. ASCII characters that are letters have a bit in their binary representation that is 0 for ...

I'm raising this on our local Meta first, rather than the main Codidact Meta, because I don't yet have the Edit Posts ability so I can't tell what problems may exist. Hopefully some of you who have...

I see the Sandbox as a vital part of challenge design. When I visit the Sandbox I'd like to be able to show only proposals that are not finalized, so I can focus feedback where it is needed. In th...

Given an integer $N$ in balanced quinary, output the first $N$ characters of your source code if $N$ is positive, or the last $-N$ characters of your source code if $N$ is negative. Terminology ...

I've recently started experimenting with hiding some of the sections in a challenge, using an expandable <details> tag. This seems to have some advantages, but I'm interested to hear how peop...

A chequer board (also spelt "checker board" in some places) is an 8 by 8 grid of squares alternating between 2 colours. Check whether a provided pattern could be a region of a chequer board. The c...

Rust, 236 184 166 142 bytes |i:u64|{let s=0x101010101010101;let(a,b,c,d)=(i&252*s,i&254*s,i&127*s,i&63*s);(i|a<<6|b<<15|c<<17|d<<10|d>>6|c>>15|b...

I'm leaving this answer here for any votes and discussion, but I no longer hold this opinion. I've posted a longer answer to explain why I've changed my mind After hearing about the filter devel...

When posting a fastest-code challenge, what do I need to bear in mind? Unlike with code-golf challenges, where the score is simply the number of bytes in the source code, for a fastest-code challe...