isleyaardvark2.rb

# This class prepares a pretty-print version of a polynomial with a minimum of 2 coefficients
#
class Polynomial
  
  # Create the polynomial object and store the coefficients
  #
  def initialize(coefficients)
    raise ArgumentError, "Need at least 2 coefficients" if coefficients.length < 2
    @coefficients = coefficients
  end

  # Returns a string version of the polynomial, simplifies coefficients of 1x^n to x^n,
  # simplifies x^1 to x and ax^0 to a. Doesn't include elements with a coefficient of 0.
  # If all coefficients = 0, returns "0".
  #
  def to_s
    polynomial = []
    @coefficients.each_with_index do |coefficient, index| 
        polynomial << coefficient.to_s + "x^" + (@coefficients.length - 1 - index).to_s
    end
    
    if @coefficients.all? { |coefficient| coefficient.zero? }
      polynomial_string = "0"
    else
      polynomial_string = polynomial.join("+")\
        .gsub(/\+\-/, '-')\
        .gsub(/(^|[\+\-])[1]x/, '\1x')\
        .gsub(/(^|[\+\-])[0]x\^[(0-9)+]/, '')\
        .gsub(/x\^1([\+\-]|$)/, 'x')\
        .gsub(/x\^0/, '')
      # ^| in regex handles case where 1x is at beginning of line, otherwise it's -1x and is covered by rest of regex
    end
    
    return polynomial_string
  end

end