# RogerBW's Blog

 The Weekly Challenge 254: Reverse the Power of Three Vowels 04 February 2024 I’ve been doing the Weekly Challenges. The latest involved numerical searching and letter substitution. (Note that this ends today.) Task 1: Three Power You are given a positive integer, `\$n`. Write a script to return true if the given integer is a power of three otherwise return false. All right, I ignored the positive bit, but so did the test cases. The obvious approach would be to take a cube root, round down to integer, and cube it, but I felt like writing a bisecting search instead. (Newton-Raphson would converge faster, but would probably need floating point.) Ruby: ``````def threepower(n0) `````` Apparently zero isn't a power of three (test cases). `````` if n0 == 0 then return false end `````` This will work for negative numbers too. `````` n = n0.abs `````` Set up the extents of the search. `````` lo = 1 hi = n.div(2) while true do `````` Find a new midpoint, and its cube. `````` t = (lo + hi).div(2) c = t * t * t `````` Is it the answer? `````` if c == n then return true end `````` Have we converged without an answer? `````` if lo == t then return false end `````` Otherwise pull the edge of the range into the midpoint and go again. `````` if c < n then lo = t else hi = t end end end `````` Task 2: Reverse Vowels You are given a string, `\$s`. Write a script to reverse all the vowels (a, e, i, o, u) in the given string. This is very easy… if you ignore case. So I chose not to. In Raku: First, a vowelness tester. ``````sub is_vowel(\$c) { if (\$c ~~ m:i/<[aeiou]>/) { return True; } else { return False; } } `````` Then the main function: ``````sub reversevowels(\$a) { `````` Break the string into a list. (I don't like subscripted string access, Python-style, though I used it in Python.) `````` my @p = \$a.comb(); `````` Have a sublist of that with just the vowels, in order. `````` my @q = @p.grep({is_vowel(\$_)}); `````` Initialise an index to point past the end of that. `````` my \$qi = @q.elems; my @o; `````` For each character: `````` for @p -> \$c { `````` If it's a vowel: `````` if (is_vowel(\$c)) { `````` Take the last unused vowel from the vowel list. `````` \$qi--; my \$nc = @q[\$qi]; `````` Flip it to match the case of the character we're looking at. `````` if (\$c eq uc(\$c)) { \$nc = uc(\$nc); } else { \$nc = lc(\$nc); } `````` Add it to the output. `````` @o.push(\$nc); } else { `````` If the character is not a vowel, add it as-is. `````` @o.push(\$c); } } return @o.join(''); } `````` 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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