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use v5.30;
use warnings;
use List::Util qw(first);
# the solution is based on my own module Quantum::Superpositions::Lazy from CPAN
use Quantum::Superpositions::Lazy;
sub first_non_repeating
{
my sub find_fnt
{
my @split = split "", shift;
# a superposition will automate some of the counting for us
my $split_pos = superpos(@split);
# the default weight for an element is 1, and weights are merged by values
my @non_repeating = grep { $_->weight == 1 } $split_pos->states->@*;
return "#" if @non_repeating == 0;
return (shift @non_repeating)->value if @non_repeating == 1;
# since we have a couple of non-repeating characters, we get the first one
# (the superposition here helps so that we solve this by a simple eq)
my $alternatives = superpos(@non_repeating);
return first { $_ eq $alternatives } @split;
}
my ($string) = @_;
my $result = "";
for (1 .. length $string) {
$result .= find_fnt(substr $string, 0, $_);
}
return $result;
}
use Test::More;
is first_non_repeating("ababc"), "aab#c";
is first_non_repeating("xyzzyx"), "xxxxx#";
is first_non_repeating("geeksforgeeksandgeeksquizfor"), "ggggggggkkksfffffffffffffora";
done_testing;
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