Hi! I am new to Perl and very stuck. I am trying to create a Perl implementation of the LCS algorithm en.wikipedia.org/wiki/Longest_common_subsequence_problem
I am required to do a comparison of two text files without the use of Text::Diff and I THINK(suggestions welcomed) this is how I should be go about it. I am having trouble converting the pseudo code functions found in the link. This is what I have so far but have no idea if I am on the right track. 


sub wikiLCSLength
{
    #$file1 = $_[0];
    #$file2 = $_[1];
    
    #$file1 = "i b c d e f g h i";
    #$file2 = "a b c d e f f f f";
    
    @m = ("a", "b", "c", "d", "e");
    @n = ("a", "b", "c", "e", "e");
    
    $mLength = scalar @m;
    $nLength = scalar @n;
    
    #Initialize the multidimensional array
    for(my $i = 0; $i<= $mLength; $i++)
    {
        for(my $j = 0; $j<= $nLength; $j++)
        {
            $C[$i][$j] = 0;
        }    
    }
    
    for($i = 0; $i <= $mLength; $i++)
    {
        $C[$i][0] = 0;
    }
    for($j = 0; $j <= $nLength; $j++)
    {
        $C[0][$j] = 0;
    }
    
    for($i=1; $i<$mLength; $i++)
    {
        for($j=1; $j<$nLength; $j++)
        {
            if($m[$i] eq $n[$j])
            {
                $C[$i][$j] = $C[$i-1][$j-1] + 1;
            } else 
            {
                $C[$i][$j] = max(($C[$i][$j-1]),($C[$i-1][$j]));
            }
        }
    
    }
    

    &wikiBacktrack(\@C, \@m, \@n, $mLength, $nLength);
}

sub wikiBacktrack
{
    @C = @{$_[0]};
    @m = @{$_[1]};
    @n = @{$_[2]};
    $mLength = $_[3];
    $nLength = $_[4];
    
    print("\n $n[5] \n");
    
    #BACKTRACKIN BB
    if($mLength==0 || $nLength==0)
    {
        return ("");
    } elsif($m[$mLength] eq $n[$nLength])
    {    
        return &wikiBacktrack(@C, @m, @n, $mLength-1, $nLength-1) + $m
+[$mLength];
    } else  
    {
        if($C[$mLength][$nLength-1] > $C[$mLength-1][$nLength])
        {
            return &wikiBacktrack(@C, @m, @n, $mLength, $nLength-1);
        } else
        {
            return &wikiBacktrack(@C, @m, @n, $mLength-1, $nLength);
        }
    }
}

[download]

Any help would be greatly appreciated. Thanks in advance!

In reply to LCS algorithm by porl

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