Created
December 25, 2011 05:43
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愚直なエラトステネスのふるい(動きがわかるよ)
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ns = Array.new(99){|i| i+2} | |
result = Array.new | |
while ns.length != 0 | |
prime = ns.shift | |
ns.delete_if{|x| x % prime == 0} | |
result.push prime | |
p ns | |
p result | |
puts | |
end |
本当は、すべての数について走査する必要はない。高々100の平方根までで問題ない
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エラトステネスの篩です。