difference_sum_squares

difference_sum_squares.rb

def difference_sum_square(number)
  sum_squared = 0
  number.times do |num|
    sum_squared += num + 1  
  end
  sum_squared = sum_squared ** 2 

  square_sums = 0
  number.times do |num|
    square_sums += (num + 1) ** 2
  end    

  sum_squared - square_sums
end

puts difference_sum_square(100)

difference_sum_squares_spec.rb

require 'rspec'
require 'difference_sum_squares'

describe 'difference_sum_square' do
  it 'returns the difference between 1 squared and the sum of 1, sqaured' do
    difference_sum_square(1).should eq 0
  end

  it 'returns the difference for the number 2' do
    difference_sum_square(2).should eq 4
    difference_sum_square(10).should eq 2640
  end 

  it 'returns the difference for the number 100' do
    difference_sum_square(100).should eq 25164150
  end
end