21 lines
333 B
Ruby
21 lines
333 B
Ruby
def solution_4(digits)
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min = min(digits)
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max = max(digits)
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(min..max)
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.to_a
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.map { |i| (min..max).to_a.map { |j| i * j } }
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.flatten(1)
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.select { |i| i.to_s == i.to_s.reverse }
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.sort
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.last
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end
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def min(digits)
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("1" + "0" * (digits - 1)).to_i
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end
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def max(digits)
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("1" + "0" * (digits)).to_i - 1
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end
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