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require 'prime'
#The prime factors of 13195 are 5, 7, 13 and 29.
#What is the largest prime factor of the number 600851475143 ?
class OptimusPrime
def factors_of(number)
return [] if number == 1
lowest_prime = 1
each do |prime|
if number % prime == 0
lowest_prime = prime
break
end
end
([lowest_prime] + factors_of(number / lowest_prime)).flatten
end
private
def each(&block)
Prime.each(&block)
end
end
describe 'problem three' do
subject { OptimusPrime.new }
it 'returns prime factorization' do
expect(subject.factors_of(13195)).to match_array([5, 7, 13, 29])
end
it 'returns the answer' do
expect(subject.factors_of(600851475143)).to match_array([71, 839, 1471, 6857])
end
it 'returns the answer to 65' do
expect(subject.factors_of(65)).to match_array([5, 13])
end
it 'returns the answer to 38' do
expect(subject.factors_of(38)).to match_array([2, 19])
end
it 'returns the answer to 48' do
expect(subject.factors_of(48)).to match_array([2, 2, 2, 2, 3])
end
it 'returns the answer to 64' do
expect(subject.factors_of(64)).to match_array([2, 2, 2, 2, 2, 2])
end
end
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