#! perl -slw
use strict;

sub lcs_arrays1 {
    my ( $a1, $a2 ) = @_;
    my @matches;
    my $longest = 0;
    my @last;
    my @this;

    for my $b1 ( 0 .. $#$a1 ) {
        @this = @last;
        @last = ();

        for my $b2 ( 0 .. $#$a2 ) {
            if ( $$a1[$b1] eq $$a2[$b2] ) {
                my @match = ( $$a1[$b1] );
                my $e2 = $b2+1;

                $this[$e2] = $last[$e2-1] + 1;

                if ($this[$e2] > $longest) {
                    $longest = $this[$e2];
                    @matches = ();
                }

                if ($this[$e2] == $longest) {
                    push @matches, [
                       @{$a1}[ ($b1-$longest+1), $b1 ]
                    ];
                }
            }
        }
    }

    return $matches[0]; # array ref -> longest matching list
}

sub lcs_arrays2 {
    my ( $a1, $a2 ) = @_;
    my @match;
    my $longest = 0;
    my @last;
    my @this;

    for my $b1 ( 0 .. $#$a1 ) {
        @this = @last;
        @last = ();

        for my $b2 ( 0 .. $#$a2 ) {
            if ( $$a1[$b1] eq $$a2[$b2] ) {
                my @match = ( $$a1[$b1] );
                my $e2 = $b2+1;

                $this[$e2] = $last[$e2-1] + 1;

                if ($this[$e2] > $longest) {
                    $longest = $this[$e2];
                    @match = @{$a1}[ ($b1-$longest+1), $b1 ];
                }
            }
        }
    }

    return \@match; # array ref -> longest matching list
}

my @a = ( 'a'..'d' );
my @b = ( 'b'..'d' );

print 'v1: ',  @{ lcs_arrays1( \@a, \@b ) };
print 'v2: ',  @{ lcs_arrays2( \@a, \@b ) };

__END__
C:\test\690326>ikegami.pl
Use of uninitialized value in addition (+) at C:\test\690326\ikegami.pl line 20.
Use of uninitialized value in addition (+) at C:\test\690326\ikegami.pl line 20.
Use of uninitialized value in addition (+) at C:\test\690326\ikegami.pl line 20.
v1: bb
Use of uninitialized value in addition (+) at C:\test\690326\ikegami.pl line 55.
Use of uninitialized value in addition (+) at C:\test\690326\ikegami.pl line 55.
Use of uninitialized value in addition (+) at C:\test\690326\ikegami.pl line 55.
v2: