# 1ashiv's solution

## to Prime Factors in the Ruby Track

Published at Dec 05 2019 · 0 comments
Instructions
Test suite
Solution

Compute the prime factors of a given natural number.

A prime number is only evenly divisible by itself and 1.

Note that 1 is not a prime number.

## Example

What are the prime factors of 60?

• Our first divisor is 2. 2 goes into 60, leaving 30.
• 2 goes into 30, leaving 15.
• 2 doesn't go cleanly into 15. So let's move on to our next divisor, 3.
• 3 goes cleanly into 15, leaving 5.
• 3 does not go cleanly into 5. The next possible factor is 4.
• 4 does not go cleanly into 5. The next possible factor is 5.
• 5 does go cleanly into 5.
• We're left only with 1, so now, we're done.

Our successful divisors in that computation represent the list of prime factors of 60: 2, 2, 3, and 5.

You can check this yourself:

• 2 * 2 * 3 * 5
• = 4 * 15
• = 60
• Success!

For installation and learning resources, refer to the Ruby resources page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

``````gem install minitest
``````

If you would like color output, you can `require 'minitest/pride'` in the test file, or note the alternative instruction, below, for running the test file.

Run the tests from the exercise directory using the following command:

``````ruby prime_factors_test.rb
``````

To include color from the command line:

``````ruby -r minitest/pride prime_factors_test.rb
``````

## Source

The Prime Factors Kata by Uncle Bob http://butunclebob.com/ArticleS.UncleBob.ThePrimeFactorsKata

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### prime_factors_test.rb

``````require 'minitest/autorun'
require_relative 'prime_factors'

class PrimeFactorsTest < Minitest::Test
def test_1
assert_equal [], PrimeFactors.of(1)
end

def test_2
skip
assert_equal [2], PrimeFactors.of(2)
end

def test_3
skip
assert_equal [3], PrimeFactors.of(3)
end

def test_4
skip
assert_equal [2, 2], PrimeFactors.of(4)
end

def test_6
skip
assert_equal [2, 3], PrimeFactors.of(6)
end

def test_8
skip
assert_equal [2, 2, 2], PrimeFactors.of(8)
end

def test_9
skip
assert_equal [3, 3], PrimeFactors.of(9)
end

def test_27
skip
assert_equal [3, 3, 3], PrimeFactors.of(27)
end

def test_625
skip
assert_equal [5, 5, 5, 5], PrimeFactors.of(625)
end

def test_901255
skip
assert_equal [5, 17, 23, 461], PrimeFactors.of(901_255)
end

def test_93819012551
skip
assert_equal [11, 9539, 894_119], PrimeFactors.of(93_819_012_551)
end
end``````
``````=begin
Write your code for the 'Prime Factors' exercise in this file. Make the tests in
`prime_factors_test.rb` pass.

To get started with TDD, see the `README.md` file in your
`ruby/prime-factors` directory.
=end
class PrimeFactors
def self.of(number)
return [] if number <= 1

return [number] if number <= 3

result = []
div = 2
while number > 1
if (number % div).zero?
number /= div
result << div
else
div += 1
end
end
result
end
end``````

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