24 lines
444 B
Ruby
24 lines
444 B
Ruby
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def triangular
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triangular_enum = Enumerator.new do |y|
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n = 1
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loop do
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x = n * (n+1) / 2
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n += 1
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y << x
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end
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end
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triangular_enum
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end
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def pentagonal?(n)
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((Math.sqrt((24 * n) + 1) + 1) / 6) % 1 == 0
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end
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def hexagonal?(n)
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((Math.sqrt((8 * n) + 1) + 1) / 4) % 1 == 0
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end
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def triangular_pentagonal_and_hexagonal_up_to(n)
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triangular.take_while { |x| x < n }.select { |x| pentagonal?(x) && hexagonal?(x) }
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end
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