# RogerBW's Blog

 The Weekly Challenge 261: Two Elements Who Adore You 24 March 2024 I’ve been doing the Weekly Challenges. The latest involved digit sums and progressive multiplication. (Note that this ends today.) Task 1: Element Digit Sum You are given an array of integers, @ints. Write a script to evaluate the absolute difference between element and digit sum of the given array. For example, `1, 2, 3, 45` differs in that the digit sum of 45 is 9, so the result is 36. So the obvious approach would be to work out the element sum of the list, and the digit sum of the list. But it occurred to me that there was an easier, or at least a more enjoyable, way to do it. Considering each element: If there's only one digit, we can ignore it. If there are two digits, say `yx`, then we can ignore the `x`, and the contribution to the total difference will be `y × 9`. If there's a third digit, so it's `zyx`, the difference contributed by the first place will be `z × 99`. (And the original value will never be less than the digit sum.) Therefore in Python: ``````def elementdigitsum(a): delta = 0 for n0 in a: `````` We'll never care about the final digit. `````` n = n0 // 10 `````` Set a multiplier term. `````` m = 10 `````` While we have some non-zero digits: `````` while n > 0: `````` Add the contribution of the last one. `````` delta += (n % 10) * (m - 1) `````` Divide, increase the multiplier, and continue. `````` n //= 10 m *= 10 return delta `````` The other languages work basically identically. Task 2: Multiply by Two You are given an array of integers, `@ints` and an integer `\$start`. Write a script to do the followings: a) Look for `\$start` in the array `@ints`, if found multiply the number by 2 b) If not found stop the process otherwise repeat In the end return the final value. Which seems to me quite readily expressed as: "while the value is in the list, double it and start again". In Raku: ``````sub multiplybytwo(@a, \$start) { `````` Build a set of the values in `@ints`. `````` my %p = Set(@a); `````` Set the result to the initial value. `````` my \$v = \$start; `````` Loop while that value is in the list. `````` while (%p{\$v}:exists) { `````` And double it. `````` \$v *= 2; } return \$v; } `````` In PostScript we can do it with just one variable, without straining understanding terribly hard. ``````/multiplybytwo { 0 dict begin exch /p exch toset def { dup p exch known { 2 mul } { exit } ifelse } loop end } bind def `````` 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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