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So this is how I spent my Friday night before bedtime, solving a problem on Exercism.

#### This is the problem

###### Raindrops

Write a program that converts a number to a string, the contents of which depends on the number's prime factors.

- If the number contains 3 as a prime factor, output 'Pling'.
- If the number contains 5 as a prime factor, output 'Plang'.
- If the number contains 7 as a prime factor, output 'Plong'.
- If the number does not contain 3, 5, or 7 as a prime factor, just pass the number's digits straight through.

###### Examples

- 28's prime-factorization is 2, 2, 7.
- In raindrop-speak, this would be a simple "Plong".

- 1755 prime-factorization is 3, 3, 3, 5, 13.
- In raindrop-speak, this would be a "PlingPlang".

- The prime factors of 34 are 2 and 17.
- Raindrop-speak doesn't know what to make of that, so it just goes with the straightforward "34".

#### My solution (not the best but will go through another iteration)

```
class Raindrops
RAINDROPS = {
'3' => 'Pling',
'5' => 'Plang',
'7' => 'Plong'
}
def self.convert(prime_num)
if prime_num == 1
return prime_num.to_s
else
primes = find_prime_factors(prime_num)
end
drops = primes.map { |p| RAINDROPS[p.to_s] }.join
drops.empty? ? prime_num.to_s : drops
end
def self.find_prime_factors(num)
primes = []
(2..num).each do |n|
if(num % n == 0)
primes << n if is_prime?(n)
end
end
primes
end
def self.is_prime?(num)
(2..(Math.sqrt(num).ceil)).each do |n|
return false if (num % n == 0)
end
end
end
```

Yes, I do realise there is a Prime class that I could use, but I didn't want to. If you haven't checkout Exercism already, you're still not too late to the party.