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- #!/usr/bin/ruby
- # Daniel "Trizen" Șuteu
- # Edited: 04 November 2017
- # https://github.com/trizen
- # How many circular primes are there below one million?
- # https://projecteuler.net/problem=35
- # Runtime: 0.999s (previously 1.235s)
- var count = 4 # number of circular primes < 10
- var limit = 1e6
- for (var p = 11; p < limit; p.next_prime!) {
- var s = Str(p)
- next if s.contains(/[^1379]/)
- var d = s.chars
- if (d.range.all {|k| Num(d.rotate(k).join).is_prime }) {
- ++count
- }
- }
- say count
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