# RogerBW's Blog

 The Weekly Challenge 198: Count Max 08 January 2023 I’ve been doing the Weekly Challenges. The latest involved analysing a list and counting primes. (Note that this is open until the end of today.) The Challenge-adjacent programming I did first was a metatest generator. Given a set of tests, which I translated into a YAML-based format, like: ``````--- ch-1: - function: maxgap arguments: - 2 - 5 - 8 - 1 result: 2 - function: maxgap arguments: - 3 result: 0 ch-2: - function: primecount arguments: 10 result: 4 - function: primecount arguments: 15 result: 6 - function: primecount arguments: 1 result: 0 - function: primecount arguments: 25 result: 9 `````` it can automatically generate the boilerplate files for each challenge in each language, with the tests already laid out (with arrays and strings and so on delimited appropriately for each language), just waiting for me to write the relevant solution functions. V1 was a bit ugly and non-modular; v2 seems to be working, and I plan to release it soon. On with the challenges! Task 1: Max Gap You are given a list of integers, `@list`. Write a script to find the total pairs in the sorted list where 2 consecutive elements has the max gap. If the list contains less then 2 elements then return 0. I prefer a moderately functional style, which I think is exemplified by this Kotlin: ``````fun maxgap(l0: List): Int { `````` Take care of the special case. `````` if (l0.size < 2) { return 0 } `````` Get the input values into a sorted list. `````` var l = ArrayList(l0) l.sort() `````` Calculate the gaps between pairs of values. (Yeah, could and arguably should be done with a `map`, but I didn't.) `````` var q = ArrayList() for (i in l.windowed(size = 2)) { q.add(i[1] - i[0]) } `````` Find the biggest gap. `````` val mq = q.maxOrNull()!! `````` Filter the list of gaps against that biggest one, and count the results. `````` return q.filter{it == mq}.size } `````` This varies a bit – for example Ruby has a `count` method on enumerables that takes a filter condition and returns a total, thus avoiding my having to build up an output list that I'll immediately throw away. Task 2: Prime Count You are given an integer `\$n > 0`. Write a script to print the count of primes less than `\$n`. If you already have a function to generate all primes up to a particular total, whether you've written it for previous challenges or it's available in system libraries, this becomes trivial. Perl: ``````sub primecount(\$l) { return scalar @{primes(\$l-1)}; } `````` (Though I did have to modify my standard prime generator logic to return correct lists when the maximum value is lower than 3; this hasn't been a consideration before.) Full code on github. Comments on this post are now closed. If you have particular grounds for adding a late comment, comment on a more recent post quoting the URL of this one. Search 10 per page 20 per page 50 per page 100 per page Archive Tags 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s 2010s 3d printing action advent of code aeronautics aikakirja anecdote animation anime army astronomy audio audio tech aviation base commerce battletech beer boardgaming book of the week bookmonth chain of command children chris chronicle church of no redeeming virtues cold war comedy computing contemporary cornish smuggler cosmic encounter coup covid-19 crime crystal cthulhu eternal cycling dead of winter doctor who documentary drama driving drone ecchi economics en garde espionage essen 2015 essen 2016 essen 2017 essen 2018 essen 2019 essen 2022 essen 2023 existential risk falklands war fandom fanfic fantasy feminism film firefly first world war flash point flight simulation food garmin drive gazebo genesys geocaching geodata gin gkp gurps gurps 101 gus harpoon historical history horror hugo 2014 hugo 2015 hugo 2016 hugo 2017 hugo 2018 hugo 2019 hugo 2020 hugo 2021 hugo 2022 hugo 2023 hugo 2024 hugo-nebula reread in brief avoid instrumented life javascript julian simpson julie enfield kickstarter kotlin learn to play leaving earth linux liquor lovecraftiana lua mecha men with beards mpd museum music mystery naval noir non-fiction one for the brow opera parody paul temple perl perl weekly challenge photography podcast politics postscript powers prediction privacy project woolsack pyracantha python quantum rail raku ranting raspberry pi reading reading boardgames social real life restaurant reviews romance rpg a day rpgs ruby rust scala science fiction scythe second world war security shipwreck simutrans smartphone south atlantic war squaddies stationery steampunk stuarts suburbia superheroes suspense television the resistance the weekly challenge thirsty meeples thriller tin soldier torg toys trailers travel type 26 type 31 type 45 vietnam war war wargaming weather wives and sweethearts writing about writing x-wing young adult Special All book reviews, All film reviews
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