steve-g-lynn

PWC 175 Challenge 1 -- Last Sunday Challenge 1 asks us to find the last Sunday of every month in a particular year, say 2022. This is easy to do in Perl thanks to the Date::Manip suite of modules, which bristles with options, including a straightforward way to do this. The specific module useful here is Date::Manip::Recur With this module it's as easy as saying: $date_recur_object -> parse( " last Sunday of every month in 2022 " ); which is exactly what I do. In Raku, it's a bit more difficult, but still easy via Raku's excellent and well-documented built-in Date objects. Pretty much a matter of looping through the last 10 days of each month, picking up the Sundays in that stretch, and then keeping the last Sunday. Julia is similar to Raku in its Dates handling, except that the Dates are not built-in, but a short library call away. I could have translated my Raku script line-for-line to Julia, but I have the minor difference that I used multiple dispatch in R...

PWC #174 Challenge 1 (Disarium Numbers) For challenge 1, we are tasked to find the first 19 disarium numbers . These are base-ten positive integers "abc..." such that a^1+b^2+c^3 ... = abc... (I don't know how to type Math in this blog platform, so I use something like Excel formula syntax, with which readers should be familiar) For example, 518 is a disarium number, because 5+1^2+8^3 = 518.  There are only 20 disarium numbers, with the 20th being a 20-digit monster. The first 10 are mechanically the single-digit numbers from 0 through 9. The 19th is a 7-digit number around 2.6 million. I used a brute-force approach of just going through all the numbers from 0 to 3_000_000, and selecting the ones which meet the disarium condition. But a more efficient strategy exists, which I sketch below, but did not implement in most of my scripts. The brute force approach is fast enough for the first 19 items. More efficient algorithm (but I use brute force for my main submission) Cons...

PWC #173 Challenge 1 (Esthetic numbers) Esthetic numbers are numbers in which consecutive digits are either one less or one more than the (previous or next) other digit. For example, 5_654 is an esthetic number but 120 is not. We are asked to find a function that tells us whether a particular input number is esthetic or no. This seems like a good candidate for a regex solution, but I wound up just looping through the characters in the number (as a string) and checking if the next character was one more or less. If not, then it is not esthetic, otherwise it is. I also check that the input is numeric (otherwise not esthetic). In Perl and Raku, I check for and drop the "_" character used as a thousands separator. I have not considered single-digit numbers, the algorithm assumes the number is at least two digits (easy to fix, but I'll leave it). The internet tells me that single-digit numbers are esthetic by convention. My if condition is unnecessarily clunky, I check separa...

PWC #172 Challenge 1 (Prime Partition) The challenge calls for finding a set of n prime numbers that add up to a given number m .  CAVEAT: I have not quite followed the instructions, which require the set of primes to be distinct ("No duplicates"). My solutions also find repeated primes. Thus, the challenge gives the expected prime partition where m =19 and n =3 as: (3,5,11) where 3+5+11=19. My programs also turn up: (3,3,13) and (5,7,7). My discussion below is therefore for the somewhat different problem that allows duplicates. My bad for not reading the instructions carefully enough, but hopefully the somewhat different problem and solution is still interesting. Though usually with prior challenges, I started in Perl 5, and my Raku programs have mostly been adapted from the Perl 5 version, this time, I started in Raku.  Raku offers the combination operator, which can be used to efficiently(?) search through all combinations of items, such as an array of prime numbers. I ...