### Robbie Hatley's Solutions To The Weekly Challenge #234

For those not familiar with "The Weekly Challenge", it is a weekly programming puzzle, usually with two parts, cycling every Sunday. You can find it here:

This week (2023-09-10 through 2023-09-16) is weekly challenge #234.

Task 1 is as follows:

Task 1: Common Characters Submitted by: Mohammad S Anwar You are given an array of words made up of alphabetic characters only. Write a script to return all alphabetic characters that show up in all words, including duplicates. Example 1: Input: @words = ("java", "javascript", "julia") Output: ("j", "a") Example 2 Input: @words = ("bella", "label", "roller") Output: ("e", "l", "l") Example 3 Input: @words = ("cool", "lock", "cook") Output: ("c", "o")

My solution was to solve this by making these four subroutines:

sub is_alpha ($aref); # Return boolean indicating whether-or-not an array contains only alphabetical strings.

sub unique_letters ($aref); # Return list of unique letters in the strings of array.

sub copies ($letter, $string); # Return number of copies of $letter which exist in string.

sub min_copies ($letter, $aref); # Return minium of numbers of copies of letter in strings of array.

Then follow this algorithm for each array:

1. Make sure array is alphabetic.

2. Make an array "@letters" of the unique letters from the array.

3. Make an array "@output" to hold output.

4. For each $letter of @letters, push min_copies($letter, $aref) copies of $letter to @output.

The script I came up with was this:

Robbie Hatley's Solution to The Weekly Challenge 234-1

Task 2 is as follows:

Task 2: Unequal Triplets Submitted by: Mohammad S Anwar You are given an array of positive integers. Write a script to find the number of triplets (i, j, k) that satisfies num[i] != num[j], num[j] != num[k] and num[k] != num[i]. Example 1: Input: @ints = (4, 4, 2, 4, 3) Ouput: 18 (0, 2, 4) because 4 != 2 != 3 x 6 permutations = 6 solutions (1, 2, 4) because 4 != 2 != 3 x 6 permutations = 6 solutions (2, 3, 4) because 2 != 4 != 3 x 6 permutations = 6 solutions Total = 18 solutions. Example 2: Input: @ints = (1, 1, 1, 1, 1) Ouput: 0 (0 combinations x 0 permutations = 0 solutions) Example 3: Input: @ints = (4, 7, 1, 10, 7, 4, 1, 1) Output: 168 triplets of 1, 4, 7: 3x2×2 = 12 combinations x 6 permutations = 72 solutions triplets of 1, 4, 10: 3×2×1 = 6 combinations x 6 permutations = 36 solutions triplets of 4, 7, 10: 2×2×1 = 4 combinations x 6 permutations = 24 solutions triplets of 1, 7, 10: 3x2x1 = 6 combinations x 6 permutations = 36 solutions Total = 168 solutions

To solve this problem, I used triple-nested 3-part loops for this. But since it's not specified that i < j < k, I let all three indices travel the entire range, but insisted on $j != $i, $k != $j, $k != $i. Then in the body of the inner-most loop, I wrote:

next if $$aref[$i] == $$aref[$j] || $$aref[$j] == $$aref[$k] || $$aref[$k] == $$aref[$i];

push @unequal_index_triplets, [$i, $j, $k];

The script I ended up with is this:

Robbie Hatley's Solution to The Weekly Challenge 234-2

That's it for 234; see you on 235!

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