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Finish post for Phase I

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Dimitri Lozeve 2020-08-02 12:56:23 +02:00
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--- ---
title: "Dyalog APL Problem Solving Competition 2020 — Phase I" title: "Dyalog APL Problem Solving Competition 2020 — Phase I"
subtitle: "Annotated Solutions" subtitle: "Annotated Solutions"
date: 2020-07-31 date: 2020-08-02
toc: true toc: true
--- ---
#+begin_src default * Introduction
:Namespace Phase1
#+end_src I've always been quite fond of [[https://en.wikipedia.org/wiki/APL_(programming_language)][APL]] and its "array-oriented" approach
of programming[fn:previous-post]. Every year, [[https://www.dyalog.com/][Dyalog]] (the company
behind probably the most popular APL implementation) organises a
competition with various challenges in APL.
[fn:previous-post] See my [[./ising-apl.html][previous post]] on simulating the Ising model
with APL. It also contains more background on APL.
The [[https://www.dyalogaplcompetition.com/][Dyalog APL Problem Solving Competition]] consists of two phases:
- Phase I consists of 10 short puzzles (similar to what one can find
on [[https://projecteuler.net/][Project Euler]] or similar), that can be solved by a one-line APL
function.
- Phase II is a collection of larger problems, that may require longer
solutions and a larger context (e.g. reading and writing to files),
often in a more applied setting. Problems are often inspired by
existing domains, such as AI, bioinformatics, and so on.
In 2018, I participated in the competition, entering only Phase
I[fn:2018-competition] (my solutions are on [[https://github.com/dlozeve/apl-competition-2018][GitHub]]). This year, I
entered in both phases. I explain my solutions to Phase I in this
post. Another post will contain annotated solutions for Phase II
problems.
[fn:2018-competition] Since I was a student at the time, I was
eligible for a prize, and [[https://www.dyalog.com/nnews/128/456/Winners-Announced-for-the-2018-APL-Programming-Contest.htm][I won $100]] for a 10-line submission, which
is quite good!
The full code for my submission is on GitHub at
[[https://github.com/dlozeve/apl-competition-2020][dlozeve/apl-competition-2020]], but everything is reproduced in this
post.
* 1. Let's Split! * 1. Let's Split!
@ -87,7 +119,7 @@ output.
#+begin_quote #+begin_quote
A Microsoft Excel spreadsheet numbers its rows counting up A Microsoft Excel spreadsheet numbers its rows counting up
from 1. However Excel's columns are labelled alphabetically — from 1. However, Excel's columns are labelled alphabetically —
beginning with A–Z, then AA–AZ, BA–BZ, up to ZA–ZZ, then AAA–AAZ and beginning with A–Z, then AA–AZ, BA–BZ, up to ZA–ZZ, then AAA–AAZ and
so on. so on.
@ -222,7 +254,7 @@ Write a function that, given a right argument which is an integer
scalar or vector, returns a 1 if the values of the right argument scalar or vector, returns a 1 if the values of the right argument
conform to the following pattern (0 otherwise): conform to the following pattern (0 otherwise):
- The elements increase or stay the same until the "apex" (highest - The elements increase or stay the same until the "apex" (the highest
value) is reached value) is reached
- After the apex, any remaining values decrease or remain the same - After the apex, any remaining values decrease or remain the same
#+end_quote #+end_quote
@ -310,8 +342,3 @@ dual of Mix.] (~↓~) does:
Next, we clean this up with Ravel (~,~) and we can Mix to obtain the Next, we clean this up with Ravel (~,~) and we can Mix to obtain the
final result. final result.
#+begin_src default
:EndNamespace
#+end_src