5kyu: add primes in numbers

Signed-off-by: Matej Focko <mfocko@redhat.com>

5kyu/primes_in_numbers/solution.rb

@@ -0,0 +1,32 @@
+def get_power_and_remainder(n, p)
+  q = 0
+  while n % p == 0 do
+    n /= p
+    q += 1
+  end
+
+  [n, q]
+end
+
+def format_prime_factor(p, q)
+  case q
+  when 0
+    ""
+  when 1
+    "(" + p.to_s + ")"
+  else
+    "(" + p.to_s + "**" + q.to_s + ")"
+  end
+end
+
+def prime_factors(n)
+  result = (2..Math.sqrt(n) + 1).reduce("") { |factors, p|
+    n, q = get_power_and_remainder(n, p)
+    factors + format_prime_factor(p, q)
+  }
+
+  if n > 1 then
+    result += format_prime_factor(n, 1)
+  end
+  result
+end

README.md

@@ -116,6 +116,7 @@
 ### Ruby
 
 - [Best travel](https://www.codewars.com/kata/55e7280b40e1c4a06d0000aa) - [solution](5kyu/best_travel)
+- [Primes in numbers](https://www.codewars.com/kata/54d512e62a5e54c96200019e) - [solution](5kyu/primes_in_numbers)
 
 ## 6 kyu