35 lines
770 B
Ruby
35 lines
770 B
Ruby
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# Least-significant-digit first string sort of fixed-length ASCII strings,
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# linear-time sort in typical cases.
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# See examples in test/lsd_test.rb
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module LSD
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RADIX = 256
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def self.sort(strings, length)
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(length - 1).downto(0).each do |i|
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counts = Array.new(RADIX + 1, 0)
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# compute frequency counts
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strings.each do |string|
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ch = string[i].ord
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counts[ch + 1] += 1
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end
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# transform counts into indices
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(1..RADIX).each { |r| counts[r] += counts[r - 1] }
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# distribute it
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aux = Array.new(strings.length)
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strings.each do |string|
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ch = string[i].ord
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aux[counts[ch]] = string
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counts[ch] += 1
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end
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# and copy back
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strings = aux
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end
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strings
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end
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end
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