Robbie's Perl Programming Blog

For those not familiar with "The Weekly Challenge", it is a weekly programming puzzle with two parts, with a new pair of tasks each Monday. You can find it here: The Weekly Challenge The Weekly Challenge for the week of 2026-09-14 through 2026-09-20 is #391. The tasks for challenge #391 are as follows: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Task 391-1: Array Median Submitted by: Mohammad Sajid Anwar You are given two sorted arrays of numbers. Write a script to merge the two given sorted arrays and return the median of the merged array. "Merging" is just "my @a3 = sort {$a<=>$b} (@$a1, @$a2);". (Merge Sort won't work, because the problem doesn't state whether the arrays are increasing, decreasing, or going in opposite directions. So I force increasing.) "Median" depends on parity. For an odd number of elements, the median is the middle element. For an even number of elements, the median is one ha...

For those not familiar with "The Weekly Challenge", it is a weekly programming puzzle with two parts, with a new pair of tasks each Monday. You can find it here: The Weekly Challenge The Weekly Challenge for the week of 2026-09-07 through 2026-09-13 is #390. The tasks for challenge #390 are as follows: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Task 390-1: Decode String Submitted by: Mohammad Sajid Anwar You are given an encoded string. Write a script to return the decoded string of the given encoded string. The encoding rule is: K[encoded_string], where the encoded_string inside the square brackets is repeated exactly K > 0 times. I'll use a Perl s/// operator in a while loop to decode innermost bracket pairs for as long as some exist, thus solving the problem from the inside out. Robbie Hatley's Perl Solution to The Weekly Challenge 390-1 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Task 39...

For those not familiar with "The Weekly Challenge", it is a weekly programming puzzle with two parts, with a new pair of tasks each Monday. You can find it here: The Weekly Challenge The Weekly Challenge for the week of 2026-08-31 through 2026-09-07 is #389. The tasks for challenge #389 are as follows: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Task 389-1: Reorder Notes Submitted by: Reinier Maliepaard You are given an array [composer, notes, permutation]. Reconstruct the melody by using each permutation value as the destination position of the corresponding note. Use no explicit for, foreach, or while loops. Output each result as "COMPOSER => reordered notes". ASSUMPTION: Input is valid; the notes array and permutation array have identical lengths, and the permutation contains each position from 1 to N exactly once. I solved this by assigning the original array to an initially-empty array "sliced" by the permutation numb...

For those not familiar with "The Weekly Challenge", it is a weekly programming puzzle with two parts, with a new pair of tasks each Monday. You can find it here: The Weekly Challenge The Weekly Challenge for the week of 2026-08-24 through 2026-08-30 is #388. The tasks for challenge #388 are as follows: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Task 388-1: Dyck Words Submitted by: Mohammad S Anwar A Dyck Word of order $n is a string of length 2x$n consisting of $n ‘U’ (Up) characters and $n ‘D’ (Down) characters such that no initial prefix of the string contains more ‘D’s than ‘U’s. Write a script to return a list of all valid Dyck words of length 2x$n, sorted in lexicographical (alphabetical) order. I first generate likely candidate equivalent integers (with the correct number of binary digits, beginning with 1 and ending with 0). I then check each candidate to see if it actually is a Dyck number. For each Dyck number, I sprintf it as a binar...

For those not familiar with "The Weekly Challenge", it is a weekly programming puzzle with two parts, with a new pair of tasks each Monday. You can find it here: The Weekly Challenge The Weekly Challenge for the week of 2026-08-17 through 2026-08-23 is #387. The tasks for challenge #387 are as follows: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Task 387-1: Rearrange Binary String Submitted by: Mohammad Sajid Anwar You are given a binary string. Write a script to re-arrange the string that all occurrences of “01” are simultaneously replaced with “10” until no occurrences of “01” exist. Return the total steps needed. I'll use a s///g operator in a while loop and count how many times it runs. Robbie Hatley's Perl Solution to The Weekly Challenge 387-1 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Task 387-2: Atoms Count Submitted by: Mohammad Sajid Anwar You are given a chemical formula with element...

For those not familiar with "The Weekly Challenge", it is a weekly programming puzzle with two parts, with a new pair of tasks each Monday. You can find it here: The Weekly Challenge The Weekly Challenge for the week of 2026-08-10 through 2026-08-16 is #386. The tasks for challenge #386 are as follows: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Task 386-1: Reverse Base Submitted by: Mohammad Sajid Anwar You are given a string representing a number, and an integer specifying the base of that representation. Write a function to convert this string to an integer. (For bases greater than 10, use characters A-Z, a-z, + and / in that order.) This is basically a repeat of 384, so I'll just re-use that solution, which uses the base conversion routines in Math::BigInt. Though, I'll have to make some minor tweaks to allow for the collation sequence specified in 386. Robbie Hatley's Perl Solution to The Weekly Challenge 386-1 ...