I guess the time complexity is 5 * O(n)

Sloow!

Sorry. I didn't thought that I'd need to use the spoiler flag when commenting in the soulutions section.

How could one know if price_per_kg should be in float. I finnaly gave up.

What's printed in expected when running test cases in not accurate either.

What's the point of decimal point in 1./?

Nice.

Good kata. I wonder which one is the better appraoch, using a char array, vs int or long array to hold the digits?

My code seems to return the expected results, but it fails with:

(compared using ==)

Diff:
@@ -11,7 +11,7 @@
   :card_number=>"1234-2121-1221-1211",
   :transaction_date=>#<Date: 2010-08-21 ((2455430j,0s,0n),+0s,2299161j)>},
  {:id=>13,
-  :name=>"[product name not found]",
+  :name=>"product name not found",
   :price=>76.05,

And for:

-  :card_name=>"[card name not found]",
+  :card_name=>"card name not found",

But I don't see any difference in the diff.

Finally done. Thanks to the author, learned a lot about primes.

This could only generate about 4 million.

Java Translation

I solved this. But I'm not sure if I followed the best approach. Is this belong to any specific type of problems? Please let me know if there are any references that worth following.