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36 lines
604 B
36 lines
604 B
def solve(n, debug: false)
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elves = Array.new(n) {|i| i+1 }
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until elves.size == 1
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across = elves.size / 2
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elves.delete_at(across)
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elves.rotate!
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end
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elves.first
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end
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# This takes too long
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# n = 3017957
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# puts solve(n)
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# So instead use this to find the pattern!
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(1..100).each do |i|
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puts "#{i}: #{solve(i)}"
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end
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# At 3**n, the counter resets
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# At 2*3**n, the counter goes up by two instead of one
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include Math
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def formula(n)
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x = log(n, 3).to_i
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a = 3**x
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b = 2*a
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(n == a) ? a : n - a + [(n - b), 0].max
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end
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(1..100).each do |n|
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puts "#{n}: #{solve(n)} #{formula(n)}"
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end
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