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Prime numbers, Ruby-style

Uses the Sieve of Eratosthenes technique, and the intruiging inject() method.
This returns an array of all the primes between 2 and 1000 inclusive.

(2..1000).inject((2..1000).to_a) {|res, i| res.select{|n|n==i||n%i!=0} }

This entry was posted on Thursday, October 12th, 2006 at 5:06 am and is filed under Ruby. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

One Response to “Prime numbers, Ruby-style”

  1. Finnbarr Murphy Says:
    October 5th, 2008 at 4:53 am

    This works well for small number range as above. However for a larger number range, say (2..10000000) the time taken is not linear O(n) or even squared O(nn) but is O((nlogn)(loglogn)).