simple diffing in ruby

diff.rb

str1 = "hello my name is jake"
str2 = "mah name is greg"

def printdiff(c, x, y, i, j)
    return if c.nil?
    if i > 0 and j > 0 and x[i] == y[j]
        printdiff(c,x,y,i-1,j-1)
        puts "  " + x[i] unless x[i].nil?
    elsif j > 0 and (i == 0 or c[i][j-1] >= c[i-1][j])
        printdiff(c,x,y,i,j-1)
        puts "+ " + y[j] unless y[j].nil?
    elsif i > 0 and (j == 0 or c[i][j-1] < c[i-1][j])
        printdiff(c,x,y,i-1,j)
        puts "- " + x[i] unless x[i].nil?
    else
        print ""
    end
end

def lcslen(a, b)
    c = Array.new(a.size + 2) { |i| Array.new(b.size + 1) { |i| 0  } }
    i = 0
    j = 0
    for i in 1..a.size do
        for j in 1..b.size do
            if a[i] == b[j]
                if ((j-1 > 0) && (i-1 > 0))
                    c[i][j] = c[i-1][j-1] + 1
                end
            else
                if (j-1 < 0 and i-1 < 0)
                    c[i][j] = [c[i][j-1], c[i-1][j]].max
                end
            end
        end
    end
    printdiff(c, a, b, i, j)
end

c = lcslen(str1.split(''), str2.split(''))

printdiff(c, str1.split(''), str2.split(''), 1, 1)