# RogerBW's Blog

 The Weekly Challenge 237: Seize Greatness 08 October 2023 I’ve been doing the Weekly Challenges. The latest involved date calculations and didn't involve array permutations. (Note that this ends today.) Task 1: Seize The Day Given a year, a month, a weekday of month, and a day of week (1 (Mon) .. 7 (Sun)), print the day. Rust's `chrono` has a built-in for this. Har har. For languages that don't: find weekday of first day of month find date of first desired weekday in month add 7 per subsequent week count check whether this is still in the same month Raku: ``````sub seizetheday(\$year, \$month, \$weekcount, \$dayofweek) { `````` Start at the first day of the month. `````` my \$dt = Date.new(year => \$year, month => \$month, day => 1); `````` Get its weekday. `````` my \$wd = \$dt.day-of-week; `````` If that's not the weekday we want, move it forward to the first one that is. `````` if (\$wd != \$dayofweek) { \$dt = \$dt.later(days => (\$dayofweek - \$wd + 7) % 7); } `````` Then if we want a later X-day, step forward by weeks. `````` if (\$weekcount > 1) { \$dt = \$dt.later(weeks => (\$weekcount - 1)); } `````` If this modified date isn't in the same month and year as the original, return zero. `````` if (\$dt.month != \$month || \$dt.year != \$year) { return 0; } `````` Return the day of the month. `````` return \$dt.day; } `````` Lua and PostScript don't have date libraries. Well, they do now. All it really needs is a converter from y-m-d to Julian date, a converter the other way—both of which you can readily build from the formulae on the Wikipedia page—and a day-of-week calculator which is essentially Julian date mod 7 with an offset. Kotlin and Scala, both using the Java `time` library, end up looking almost identical. Task 2: Maximise Greatness You are given an array of integers. Write a script to permute the give array such that you get the maximum possible greatness. To determine greatness, `nums[i] < perm[i]` where ```0 <= i < nums.length``` The hardest part here is the description of the problem, because it might lead one astray into actually trying permutations. First, sort the list. Then have a pair of pointers, let's call them `lead` and `lag`; start both at zero. Run `lead` over each list element. If the value there is greater than the value at `lag`, increment `lag` by one. (Because the list is sorted, this is the lowest possible `lead` value that's greater than the `lag` value.) The final value of `lag` is the greatness. In practice we aren't using C so `lead` is implemented as an iterator over the sorted list. Ruby: ``````def maximisegreatness(a) b = a.sort g = 0 b.each do |c| if c > b[g] then g += 1 end end return g end `````` 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
Produced by aikakirja v0.1