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36 lines
679 B
Ruby
36 lines
679 B
Ruby
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# The Computer Language Shootout
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# http://shootout.alioth.debian.org/
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#
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# contributed by Glenn Parker, March 2005
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# modified by Evan Phoenix, Sept 2006
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def sieve(m)
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flags = Flags.dup[0,m]
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count = 0
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pmax = m - 1
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p = 2
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while p <= pmax
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unless flags[p].zero?
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count += 1
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mult = p
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while mult <= pmax
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flags[mult] = 0
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mult += p
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end
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end
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p += 1
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end
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count
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end
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n = 9 # (ARGV[0] || 2).to_i
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Flags = ("\x1" * ( 2 ** n * 10_000)).unpack("c*")
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n.downto(n-2) do |exponent|
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break if exponent < 0
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m = (1 << exponent) * 10_000
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# m = (2 ** exponent) * 10_000
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count = sieve(m)
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printf "Primes up to %8d %8d\n", m, count
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end
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