Binomial Coefficients by Dynamic Programming, Using Ruby

Source.rb

class Table
  def initialize(n, firstValue)
    @m = {}
    (0...n).each do |i|
      @m[i] = {}
      (0...n).each do |j|
        @m[i][j] = firstValue
      end
    end
  end

  def gs(i,j, v = nil)
    raise "#{i} #{j}" if @m[i].nil?
    if v
      @m[i][j] = v
    else
      @m[i][j]
    end
  end
end

#
# (n k) where
#
def binomial_coefficient(n, k, show_triangle = false)
  raise "n cannot be greater than 100 for this solution" if n >= 100
  raise "k cannot be greater than n" if k > n
  return 1 if (n == 0 || k == n)

  t = Table.new(n+1, 0)
  (0...(n+1)).each { |i| t.gs(i,0,1) }
  (1...(n+1)).each { |ij| t.gs(ij,ij,1) }

  (1...(n+1)).each do |i|
    (1...i).each do |j|
      t.gs(i,j,t.gs(i-1,j-1) + t.gs(i-1,j))
    end
  end

  (0...(n+1)).each { |i| puts (0..i).map { |j| t.get(i,j) }.join(' ') } if show_triangle
  t.gs(n,k)
end