pwc-074-fnr-and-me.pl

#!/usr/bin/perl
use v5.14;

sub fnr_chars {
    my $str = shift;
    my @nr;
    my %h;
    join '', map {
        push @nr, $_ if not exists $h{$_};
        $h{$_}++;
        my $f;
        while (@nr) {
            $f = $nr[$#nr];
            last if $h{$f} == 1;
            pop @nr;
            $f = undef;
        }
        $f // '#';
    } split '', $str;
}

say fnr_chars('ababc');
say fnr_chars('xyzzyx');

my @A = (1, 2, 2, 3, 2, 4, 2);
my @B = (1, 3, 1, 2, 4, 5);

sub majority_el {
    my $arr_ref = shift;
    my %h;
    $h{$_}++ for @$arr_ref;
    my ($major) = grep {$h{$_} > @$arr_ref / 2} keys %h;
    $major // -1;
}

say majority_el(\@A);
say majority_el(\@B);