Project Euler #17

Euler Project #17: "If the numbers 1 to 5 are written out in words: one, two, three, four, five, then there are 3 + 3 + 5 + 4 + 4 = 19 letters used in total.

"If all the numbers from 1 to 1000 (one thousand) inclusive were written out in words, how many letters would be used?"

Their notes say something about "and" in numbers British-style, but I have ignored this as I have no idea where the ands would go.

	use v6;
	my %number_names = (
	1 => "one",
	2 => "two",
	3 => "three",
	4 => "four",
	5 => "five",
	6 => "six",
	7 => "seven",
	8 => "eight",
	9 => "nine",
	10 => "ten",
	11 => "eleven",
	12 => "twelve",
	13 => "thirteen",
	14 => "fourteen",
	15 => "fifteen",
	16 => "sixteen",
	17 => "seventeen",
	18 => "eighteen",
	19 => "nineteen",
	20 => "twenty",
	30 => "thirty",
	40 => "forty",
	50 => "fifty",
	60 => "sixty",
	70 => "seventy",
	80 => "eighty",
	90 => "ninety"
	);
	for 1..9 -> $n
	{
	%number_names{$n * 100} = %number_names{$n} ~ " hundred";
	}
	sub NumberName(%number_names, $number)
	{
	given $number
	{
	when 0 { return "zero"; }
	when 1000 { return "one thousand"; }
	}
	my $n = $number;
	my $name = "";
	while ($n > 0)
	{
	$name ~= " " if $name.chars > 0;
	my $biggest = %number_names.keys.grep({$_ <= $n}).map({+$_}).max;
	$name ~= %number_names{$biggest};
	$n -= $biggest;
	}
	return $name;
	}
	my $letter = 0;
	for 1..1000 -> $number
	{
	my $name = NumberName(%number_names, $number);
	# say "$number => $name";
	$name.subst(rx/<alpha>/, { $letter++ }, :g);
	}
	say $letter;

view raw euler_017_01.pl hosted with ❤ by GitHub

This is a slow, stupid way to solve this problem. (Though I'm reasonably happy with it as an example of Perl 6 programming.) On the other hand, this way of doing it makes it much easier to check for correctness. (Though I discovered I'd misspelled one of the numbers in the process of posting this. Sigh.) This runs in just over 3 minutes on my MBP. I will be very disappointed if I can't get that time below 20 seconds. But that is a matter for a future post.

PS I would really like to use Yuval Kogman's system for cleaning up / speeding up Gist embedding in blog posts. Unfortunately, I can't quite make sense of what he is actually doing. Afraid I have fallen a bit behind the technological curve here...