Permutations in K

Community Support
1

I got this post :

-------- Forwarded Message --------

| Subject: | [svfig] [NSF] [ACM Members] Show off your skills in Week 8 Code Golf! |
| Date: | Tue, 17 May 2016 14:29:39 -0700 |
| From: | David L. Jaffe <dljaffe @ stanford.edu> |
| Reply-To: | David L. Jaffe <dljaffe @ stanford.edu>, Silicon Valley Forth Interest Group <svfig@zork.net> |
| To: | svfig@zork.net |

Can you do this in Forth?

Hey everyone!

ACM is hosting our next weekly code golf challenge. Just write a solution to the problem below in Python or Javascript using the fewest number of characters, and the winner gets to take home an adorable plush penguin. Deadline for submissions is Saturday, May 21 at 11:59pm!

Problem:

Write a function that takes an input string and returns a list of all permutations of that string. The string will be at most 10 characters long.

Examples:

"abc" --> ["abc", "acb", "bac", "bca", "cab", "cba"] "" --> [""]

Submit here:
http://goo.gl/forms/9EnodbZn7Pa2ccOK2

Can somebody give a succinct algorithm in K?

This is an excellent test for 4th.CoSy but I find after many years in K.CoSy ( which I still use for all my accounting ) I have been too isolated from traditional APL , in particular , JohnScholes+Dyalog path , eg : https://dfns.dyalog.com/n\_pmat.htm , much less http://www.chilton.com/~jimw/permute.html , that It’s easier to pass the question on to the K.ommunity .

Dyalog’spmat looks most interesting .

2

adapted from nsl.com

q)k)p:{x’{:$[x=1;,0;,/a,‘’(&:'~a=:a:!x)@:.z.s x-1]}[#x]}
q)p"abc"
“abc”
“acb”
“bac”
“bca”
“cab”
“cba”

3

Thanks .

Should have figured Apter might have one .

4

> a succinct algorithm in K?

here’s a different one:

k)p:{(,/@:)/,(,<<:)'x=:x:!x}

5

that’s a beauty!



added to the junk-pile, here:



http://nsl.com/k/perm.k

6

I’m very curious about this one. How does it work?

q).z.K

3.2999999999999998

q).z.k

2015.11.03

q)k)p:{(,/@:)/,(,<<:)'x=:x:!x}

q)p"abc"

k){(,/@:)/,(,<<:)'x=:x:!x}

'type

@

,<<:'

1b

q))