# ETOOBUSY ðŸš€ minimal blogging for the impatient

# PWC115 - Largest Multiple

**TL;DR**

On with TASK #2 from the Perl Weekly Challenge #115. Enjoy!

# The challenge

You are given a list of positive integers (0-9), single digit.

Write a script to find the largest multiple of 2 that can be formed from the list.

Examples`Input: @N = (1, 0, 2, 6) Output: 6210 Input: @N = (1, 4, 2, 8) Output: 8412 Input: @N = (4, 1, 7, 6) Output: 7614`

# The questions

Wellâ€¦ there are a few nitpicks:

- letâ€™s say weâ€™re focusing on single-digit inputs, not necessarily
*positive*(or`0`

would be out of the game) - letâ€™s also assume that there will
*always*be an even element in the list!

# The solution

This is the solution in Perl:

```
#!/usr/bin/env perl
use 5.024;
use warnings;
use experimental qw< postderef signatures >;
no warnings qw< experimental::postderef experimental::signatures >;
sub largest_multiple (@N) {
@N = sort { $a <=> $b } @N;
for my $i (0 .. $#N) {
if ($N[$i] % 2 == 0) {
my ($last) = splice @N, $i, 1;
return join '', reverse(@N), $last;
}
}
return;
}
my @inputs = @ARGV ? @ARGV : qw< 1 0 2 6 >;
say largest_multiple(@inputs);
```

We first sort the list bottom to top, then extract the first even item
we find. What is left will have to be reversed (so that we can find the
*largest*) and that even item put at the end. Yay!

This is the Raku version:

```
#!/usr/bin/env raku
use v6;
sub largest-multiple (@N is copy) {
@N = @N.sort: {$^a leg $^b};
for 0 ..^ @N.elems -> $i {
next if @N[$i] % 2;
@N.unshift(@N.splice($i, 1).Slip);
return @N.reverse.join('');
}
return;
}
sub MAIN (*@inputs is copy) {
@inputs = < 1 0 2 6 > unless @inputs.elems;
say largest-multiple(@inputs);
}
```

Thatâ€™s all folks!

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