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|
#!perl
###############################################################################
=comment
Perl Weekly Challenge 096, Task #2: Edit Distance
Matrix class for use in implementing the Wagner–Fischer algorithm for finding
the Levenshtein distance between two strings.
=cut
###############################################################################
#--------------------------------------#
# Copyright © 2021 PerlMonk Athanasius #
#--------------------------------------#
#==============================================================================
package Matrix;
#==============================================================================
use strict;
use warnings;
#------------------------------------------------------------------------------
sub new # Constructor
#------------------------------------------------------------------------------
{
my ($class, $word1, $word2) = @_;
my $cols = length( $word1 ) + 1;
my $rows = length( $word2 ) + 1;
my @matrix;
for my $row (0 .. $rows)
{
$matrix[ $row ][ $_ ] = undef for 0 .. $cols;
}
$word2 = "#$word2";
my $i = 0;
for my $row (1 .. $rows)
{
$matrix[ $row ][ 0 ] = substr $word2, $i, 1;
$matrix[ $row ][ 1 ] = $i++;
}
$word1 = "#$word1";
$i = 0;
for my $col (1 .. $cols)
{
$matrix[ 0 ][ $col ] = substr $word1, $i, 1;
$matrix[ 1 ][ $col ] = $i++;
}
my %self = (
height => $rows,
width => $cols,
matrix => \@matrix,
);
return bless \%self, $class;
}
#------------------------------------------------------------------------------
sub height # Accessor: getter only
#------------------------------------------------------------------------------
{
my ($self) = @_;
return $self->{height};
}
#------------------------------------------------------------------------------
sub width # Accessor: getter only
#------------------------------------------------------------------------------
{
my ($self) = @_;
return $self->{width};
}
#------------------------------------------------------------------------------
sub element # Accessor: getter and setter
#------------------------------------------------------------------------------
{
my ($self, $row, $col, $value) = @_;
if (defined $value)
{
$self->{matrix}[ $row + 1 ][ $col + 1 ] = $value; # Set
}
return $self->{matrix}[ $row + 1 ][ $col + 1 ]; # Get
}
#------------------------------------------------------------------------------
sub display
#------------------------------------------------------------------------------
{
my ($self) = @_;
my $height = $self->{height};
my $width = $self->{width};
# Pre-compute the maximum widths of individual columns
my @widths = ( 1 );
for my $col (1 .. $width)
{
my $max = 0;
for my $row (1 .. $height)
{
my $current = $self->{matrix}[ $row ][ $col ];
my $cur_len = length $current;
$max = $cur_len if $cur_len > $max;
}
$widths[$col] = $max;
}
# Draw a vertical separator
my $line = '+';
$line .= sprintf '-%s-+', '-' x $widths[ $_ ] for 0 .. $width;
$line .= "\n";
# Draw the matrix
my $display = $line;
for my $row (0 .. $height)
{
$display .= '|';
$display .= sprintf ' %*s |', $widths[ $_ ],
$self->{matrix}[ $row ][ $_ ] // ' '
for 0 .. $width;
$display .= "\n" . $line;
}
return $display;
}
###############################################################################
1;
###############################################################################
|
