# RogerBW's Blog

 The Weekly Challenge 222: Members Everywhere 25 June 2023 I’ve been doing the Weekly Challenges. The latest involved sorted lists and iterative reductions. (Note that this closes today.) Task 1: Matching Members You are given a list of positive integers, `@ints`. Write a script to find the total matching members after sorting the list increasing order. Pretty straightforward, sort and then compare. Some languages have a `zip` to merge two iterables, others don't. If they do, as in Python: ``````def matchingmembers(a): b = a.copy() b.sort() o = 0 for i in zip(a, b): if i[0] == i[1]: o += 1 return o `````` If not, as in JavaScript: ``````function matchingmembers(a) { let b = [...a]; b.sort(function(a,b) { return a-b; }); let o = 0; for (let i = 0; i < a.length; i++) { if (a[i] == b[i]) { o++; } } return o; } `````` Task 2: Last Member You are given an array of positive integers, @ints. Write a script to find the last member if found otherwise return 0. Each turn pick 2 biggest members (x, y) then decide based on the following conditions, continue this until you are left with 1 member or none. a) if x == y then remove both members b) if x != y then remove both members and add new member (y-x) My rule of thumb is that if I want the single largest entry from a list I'll use `max`, which is obviously cheaper than a full sort, but if I want two or more it's usually less faff just to `sort` it rather than messing around with a custom `max` routine. So on each pass I do that, pop the two largest entries off the end of the list, and push on a difference if it's needed. (This is always the non-negative difference, so I take advantage of the sorted list.) This looks basically the same in all languages. Perl: ``````sub lastmember(\$a0) { my @a = @{\$a0}; while (scalar @a > 1) { @a = sort {\$a <=> \$b} @a; my \$x = pop @a; my \$y = pop @a; if (\$x != \$y) { push @a, \$x - \$y; } } if (scalar @a == 0) { return 0; } else { return \$a[0]; } } `````` 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 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 2022 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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