Levenshtein distance algorithm in Ruby

lev-dist.rb

class Distance
	attr_accessor :s1, :s2
	
	def initialize(str1,str2)
		@s1 = str1
		@s2 = str2		
	end
	
	def lev_distance		
		m = @s1.length
		n = @s2.length
		d = Array.new(m+1) { Array.new(n+1) {0} }
		
		for i in 0..m
		  d[i][0] = i
		end	
		
		for j in 0..n
		  d[0][j] = j
		end
		
		for j in 1..n
		  for i in 1..m
			if (@s1[i-1] == @s2[j-1]) then
			  cost = 0
			else
			  cost = 1
			end					
			d[i][j] = [d[i-1][j]+1, d[i][j-1]+1, d[i-1][j-1] + cost].min
		  end
		end		
	
		return d[m][n]
	end
end

s1 = "kitten"
s2 = "sitting"
puts "Edit Distance between #{s1} and #{s2} is: " + Distance.new(s1,s2).lev_distance.to_s