#!/usr/local/ruby
# Pascals triangle

def fac(n)
  (1..n).inject(1) {|fac, i| fac * i}
end

def nCr(n, r)
  numerator   = fac(n)
  denominator = fac(r) * fac(n - r)
  @combinations = numerator / denominator
end

def pascal max_row

  0.upto(max_row) {|row_num|
    holder = []
    row_num.times do |ticker|
      holder << nCr(row_num, ticker)
    end
    puts holder.join(' ').center(80)
  }

end

puts 'How many rows do you want?'
max_row = gets.chomp.to_i
pascal max_row