40 lines
794 B
Ruby
40 lines
794 B
Ruby
# frozen_string_literal: true
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input = '' # TODO
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range = Range.new(*input.split('-').map(&:to_i))
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def pairwise(arr)
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arr[0...-1].zip(arr[1..])
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end
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def runs(digits)
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runs = []
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ref = digits.first
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run = ref.to_s
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digits[1..].each do |d|
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if d == ref
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run += d.to_s
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else
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runs << run
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ref = d
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run = ref.to_s
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end
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end
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runs << run
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end
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count = range.count do |n|
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# 1. All numbers in this range are six digits
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# 2. All numbers in this range are in this range
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digits = n.digits.reverse
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# 3. Two adjacent digits are the same
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double = runs(digits).any? { |run| run.length == 2 }
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# 4. Going from left to right, the digits *never decrease*
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monotonic = pairwise(digits).none? { |pair| pair.last < pair.first }
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double && monotonic
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end
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pp count
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