[euler] problem 38

Author: andreoss

categories/euler/prob038-andreoss.pl

@@ -0,0 +1,51 @@
+use v6;
+
+=begin pod
+
+=TITLE Pandigital multiples
+
+=AUTHOR Andrei Osipov
+
+L<https://projecteuler.net/problem=38>
+
+Take the number 192 and multiply it by each of 1, 2, and 3:
+
+192 × 1 = 192
+192 × 2 = 384
+192 × 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?
+
+=end pod
+
+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;
+    }
+}

t/categories/euler.t

@@ -2,7 +2,7 @@ use v6;
 
 use Test;
 
-plan 57;
+plan 58;
 
 subtest {
     plan 5;
@@ -361,6 +361,16 @@ subtest {
     check-example-solutions($problem, $expected-output, @authors)
 }, "prob036";
 
+subtest {
+    plan 1;
+
+    my $problem = "prob038";
+    my @authors = <andreoss>;
+    my $expected-output = 932718654;
+
+    check-example-solutions($problem, $expected-output, @authors)
+}, "prob038";
+
 subtest {
     plan 1;