19 lines
405 B
Crystal
19 lines
405 B
Crystal
def quickselect(a, k)
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arr = a.dup # we will be modifying it
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loop do
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pivot = arr.delete_at(rand(arr.size))
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left, right = arr.partition { |x| x < pivot }
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if k == left.size
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return pivot
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elsif k < left.size
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arr = left
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else
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k = k - left.size - 1
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arr = right
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end
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end
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end
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v = [9, 8, 7, 6, 5, 0, 1, 2, 3, 4]
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p v.each_index.map { |i| quickselect(v, i) }.to_a
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