Pandigital multiples
AUTHOR
Andrei Osipov
https://projecteuler.net/problem=38
Take the number 192 and multiply it by each of 1, 2, and 3:
192 Ć 1 = 192 192 Ć 2 = 384 192 Ć 3 = 576
By concatenating each product we get the 1 to 9 pandigital, 192384576. We will call 192384576 the concatenated product of 192 and (1,2,3)
The same can be achieved by starting with 9 and multiplying by 1, 2, 3, 4, and 5, giving the pandigital, 918273645, which is the concatenated product of 9 and (1,2,3,4,5).
What is the largest 1 to 9 pandigital 9-digit number that can be formed as the concatenated product of an integer with (1,2, ... , n) where n > 1?
use v6;
sub concat-product($x, $n) {
+ [~] do for 1...$n { $x * $_ }
}
sub is-pandigital(Int $n is copy) {
return unless 123456789 <= $n <= 987654321;
my $x = 0;
loop ( ; $n != 0 ; $n div=10) {
my $d = $n mod 10;
$x += $d * 10 ** (9 - $d);
}
$x == 123456789;
}
say max gather for 1 .. 9999 -> $x {
next if $x !~~ /^^9/;
for 2 .. 5 -> $n {
my $l = concat-product $x, $n;
take $l if is-pandigital $l;
}
}
# vim: expandtab shiftwidth=4 ft=perl6