# RogerBW's Blog

 The Weekly Challenge 256: Maximum Strings 18 February 2024 I’ve been doing the Weekly Challenges. The latest involved array analysis and string merging. (Note that this ends today.) Task 1: Maximum Pairs You are given an array of distinct words, `@words`. Write a script to find the maximum pairs in the given array. The words `\$words[i]` and `\$words[j]` can be a pair if one is the reverse of the other. The trick, of course, is that I only want to count each pair once. So I end up doing what feels like half the problem. In Raku: ``````sub maximumpairs(@a) { `````` Set up pair count and cache. `````` my \$n = 0; my \$r = SetHash.new; `````` For each word, `````` for @a -> \$s { `````` Get its reverse. `````` my \$t = \$s.flip; `````` If I've already seen the reverse, add one to the pair count. `````` if (\$r{\$t}:exists) { \$n++; `````` Otherwise, store the word in the cache so that we'll spot its reverse later. `````` } else { \$r{\$s} = 1; } } return \$n; } `````` This will be inconsistent if there are duplicates (e.g. [ba ab ab] would score 2, while [ab ab ba] would only score 1) but the problem doesn't specify how to treat those anyway. Task 2: Merge Strings You are given two strings, \$str1 and \$str2. Write a script to merge the given strings by adding in alternative order starting with the first string. If a string is longer than the other then append the remaining at the end. So it's the functionality which in many languages is called something like `zip`, but carrying on until both are exhausted rather than ending when the first one ends. I'm pretty sure Rust has an option for doing this automatically, but since I had to write the algorithm from scratch for some of the languages anyway, it was easier just to use it everywhere. JavaScript: ``````function mergestrings(a, b) { let out = ""; `````` Iterate over length of longest string. `````` for (let i = 0; i < Math.max(a.length, b.length); i++) { `````` If we haven't gone off the end of `a`, add the character from this place in `a`. `````` if (i <= a.length - 1) { out += a.substring(i, i+1); } `````` If we haven't gone off the end of `b`, add the character from this place in `b`. `````` if (i <= b.length - 1) { out += b.substring(i, i+1); } } return out; } `````` (I'm doing that classic computing thing of treating 2 as a special case of 1 rather than as a special case of infinity. An `n`-way merge would put the strings in an array and cycle over it for each character.) 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 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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