RabbitFarm

2025-02-23

Gap Minimizations

The examples used here are from the weekly challenge problem statement and demonstrate the working solution.

Part 1: Min Gap

You are given an array of integers, @ints, increasing order. Write a script to return the element before which you find the smallest gap.

The complete solution is contained in one file that has a simple structure.

"ch-1.pl" 1≡


⟨preamble 2 ⟩
⟨Min Gap subroutine. Contains all the important code for this problem. 3 ⟩
⟨main 4 ⟩
◇

For this problem we do not need to include very much. We’re just specifying to use the current version of Perl, for all the latest features in the language. This fragment is also used in Part 2.

⟨preamble 2 ⟩≡


use v5.38;
◇

Fragment referenced in 1, 5.

Let’s not even store anything. Instead go down the list and update two variables: one to store the current minimum gap, and the other to store the element before the current smallest gap found.

I use a small trick here. A way of saying The Maximum Integer is 0 + q/inf/.

⟨Min Gap subroutine. Contains all the important code for this problem. 3 ⟩≡


sub min_gap{
my($min_gap, $element_min_gap) = (0 + q/inf/, 0 + q/inf/);
{
my $x = shift @_;
my $y = shift @_;
if($x && $y){
my $gap = $y - $x;
if($gap < $min_gap){
$min_gap = $gap;
$element_min_gap = $y;
}
}
unshift @_, $y;
redo if @_ > 1;
}
return $element_min_gap;
}
◇

Fragment referenced in 1.

Now all we need are a few lines of code for running some tests.

⟨main 4 ⟩≡


MAIN:{
say min_gap 2, 8, 10, 11, 15;
say min_gap 1, 5, 6, 7, 14;
say min_gap 8, 20, 25, 28;
}
◇

Fragment referenced in 1.

Sample Run
$ perl perl/ch-1.pl 
11 
6 
28

Part 2: Min Diff

You are given an array of integers, @ints. Write a script to find the minimum difference between any two elements.

"ch-2.pl" 5≡


⟨preamble 2 ⟩
⟨Min Diff subroutine. All the code for solving the problem is here. 6 ⟩
⟨main 7 ⟩
◇

From Part 1 we know that if we sort the list we know we need to only check adjacent elements to find the minimum difference.

⟨Min Diff subroutine. All the code for solving the problem is here. 6 ⟩≡


sub min_diff{
my $min_gap = 0 + q/inf/;
my @i = sort {$a <=> $b} @_;
{
my $x = shift @i;
my $y = shift @i;
if($x && $y){
my $gap = $y - $x;
$min_gap = $gap if $gap < $min_gap;
}
unshift @i, $y;
redo if @i > 1;
}
return $min_gap;
}
◇

Fragment referenced in 5.

Finally, here’s a few tests to confirm everything is working right.

⟨main 7 ⟩≡


MAIN:{
say min_diff 1, 5, 8, 9;
say min_diff 9, 4, 1, 7;
}
◇

Fragment referenced in 5.

Sample Run
$ perl ch-2.pl 
1 
2

References

The Weekly Challenge 309
Generated Code

posted at: 19:58 by: Adam Russell | path: /perl | permanent link to this entry