# RogerBW's Blog

 The Weekly Challenge 219: Travel for Squares 04 June 2023 I’ve been doing the Weekly Challenges. The latest involved sequence processing and a cost optimisation. (Note that this is open until 4 June 2023.) Task 1: Sorted Squares You are given a list of numbers. Write a script to square each number in the list and return the sorted list, increasing order. This is mostly a one-liner, though in some languages it's easier to sort as a separate operation. Perl: ``````sub sortedsquares(\$lst) { return [sort {\$a <=> \$b} map{\$_ * \$_} @{\$lst}]; } `````` The shortest version is in PostScript, though admittedly it relies on my libraries to provide `map` and `quicksort`. ``````/sortedsquares { { dup mul } map quicksort } bind def `````` Task 2: Travel Expenditure You are given two list, @costs and @days. The list @costs contains the cost of three different types of travel cards you can buy. The list @days contains the day number you want to travel in the year. The periods of the cards are fixed at 1, 7 and 30 days, so the trick is to cover all days with one card or another at minimum total cost. Here's the JavaScript: ``````function travelexpenditure(costs, days0) { `````` Make sure the days are in order. `````` let days = days0; days.sort(function(a,b) { return a-b; }); `````` Set the validity periods. `````` const validities = [1, 7, 30]; `````` Set up the stack for a FIFO search. `````` let stack = []; stack.push([0, days]); `````` One possible cost is an individual one-day ticket for each day, so let's set that as the starting value. `````` let cheapest = days.length * costs[0]; while (stack.length > 0) { const c = stack.shift(); `````` As an entry comes off the stack, if there are no more days to cover, compare this cost with the cheapest found so far and log it if it's cheaper. `````` if (c[1].length == 0) { if (c[0] < cheapest) { cheapest = c[0]; } } else { `````` If we haven't finished but we're already costing more than the cheapest found so far, skip this leg. `````` if (c[0] >= cheapest) { continue; } `````` The first day we'll cover in this leg is the lowest remaining value. `````` const start = c[1][0]; `````` Test each possible type of card. `````` for (let i = 0; i <= 2; i++) { `````` Work out the last day for which this card will be valid. `````` const ed = start + validities[i] - 1; `````` Remaining days are those later than that one. `````` let dtd = c[1].filter(x => x > ed); `````` Push onto the stack the new cost, and the new remaining days. `````` stack.push([c[0] + costs[i], dtd]); } } } return cheapest; } `````` Since this is an exhaustive search it could have been done with a LIFO, but I felt like doing a FIFO, and at these sizes the performance loss (on languages without a dedicated double-ended array type) is very minor. 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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