31 lines
726 B
Ruby
31 lines
726 B
Ruby
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# Binary Search: This search finds an item in log(n) time provided that the container is already sorted.
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# The method returns the item if it is found, or nil if it is not. If there are duplicates, the first one
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# found is returned, and this is not guaranteed to be the smallest or largest item.
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#
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# Complexity: O(lg N)
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#
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# [1, 2, 3].binary_search(1) #=> 1
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# [1, 2, 3].binary_search(4) #=> nil
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class Array
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def binary_search(item)
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return nil if item.nil?
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low = 0
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high = self.size - 1
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while low <= high
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mid = (low + high) / 2
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val = self[mid]
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if val > item
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high = mid - 1
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elsif val < item
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low = mid + 1
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else
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return val
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end
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end
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nil
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end
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end
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