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40 lines
837 B
Ruby
40 lines
837 B
Ruby
# Top-down Mergesort algorithm based on not optimal ruby collection methods
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# just to show divide-and-conquer paradigm, uses NlgN compares to sort an array,
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# see test/merge_sort_test.rb
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class Merge
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def initialize(array)
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@array = array
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end
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def sort(array = @array)
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return array if array.length < 2
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left, right = halves(array)
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merge(sort(left), sort(right))
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end
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private
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def halves(array)
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middle = array.length / 2
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[array[0..(middle - 1)], array[middle..-1]]
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end
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def merge(first, second)
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result = []
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while first.any? || second.any?
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if first.empty?
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result << second.shift
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elsif second.empty?
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result << first.shift
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elsif first[0] > second[0]
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result << second.shift
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else
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result << first.shift
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end
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end
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result
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end
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end
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