27 lines
636 B
Ruby
27 lines
636 B
Ruby
# hailstone.rb
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module Hailstone
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module_function
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def hailstone n
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seq = [n]
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until n == 1
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n = (n.even?) ? (n / 2) : (3 * n + 1)
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seq << n
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end
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seq
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end
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end
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if __FILE__ == $0
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include Hailstone
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# for n = 27, show sequence length and first and last 4 elements
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hs27 = hailstone 27
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p [hs27.length, hs27[0..3], hs27[-4..-1]]
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# find the longest sequence among n less than 100,000
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n, len = (1 ... 100_000) .collect {|n|
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[n, hailstone(n).length]} .max_by {|n, len| len}
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puts "#{n} has a hailstone sequence length of #{len}"
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puts "the largest number in that sequence is #{hailstone(n).max}"
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end
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