#!/usr/bin/env perl

use strict;
use warnings;
use v5.22;
use List::Util qw( min max );

sub get_filehandle {
    if (@ARGV !=1) {
        die "Usage: $0 [input-filename]";
    }
    my $input_filename = $ARGV[0];
    open my $filehandle, '<', $input_filename or
        die "Could not open input file $input_filename: $!";
    return $filehandle;
}

sub get_numbers {
    my $fh = shift;
    chomp( my $numbers = ( <$fh> ) );
    return (split( ",", $numbers));
}

# Advent of Code 2021 Day 07
my $filehandle  = get_filehandle();
my @numbers     = get_numbers($filehandle);
my $min_fuel_cost;
my $horiz_pos;
my $low = min(@numbers);
my $high = max(@numbers);

foreach my $x ($low .. $high) {
    my $fuel_cost = 0;
    foreach my $y (0 .. $#numbers) {
        my $n = abs($x - $numbers[$y]);
        $fuel_cost += $n * ($n + 1) / 2;
    }
    if (!defined($min_fuel_cost) || $fuel_cost < $min_fuel_cost) {
        $min_fuel_cost = $fuel_cost;
        $horiz_pos = $x;
    }
}

say "winning position is $horiz_pos with cost of $min_fuel_cost";