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* Retranslate the complete English edition from Simplified Chinese * Polish three English explanations after reader-focused review
48 lines
1.5 KiB
Ruby
48 lines
1.5 KiB
Ruby
=begin
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File: binary_search_edge.rb
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Created Time: 2024-04-09
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Author: Blue Bean (lonnnnnnner@gmail.com)
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=end
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require_relative './binary_search_insertion'
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### Find the leftmost occurrence of target using binary search ###
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def binary_search_left_edge(nums, target)
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# This is equivalent to finding the insertion point of target
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i = binary_search_insertion(nums, target)
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# If target was not found, return -1
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return -1 if i == nums.length || nums[i] != target
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i # Target was found; return index i
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end
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### Find the rightmost occurrence of target using binary search ###
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def binary_search_right_edge(nums, target)
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# For integer elements, find the leftmost insertion point of target + 1
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i = binary_search_insertion(nums, target + 1)
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# i is the index of the first element greater than target (or the array length); j is the candidate rightmost target index
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j = i - 1
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# If target was not found, return -1
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return -1 if j == -1 || nums[j] != target
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j # Target was found; return index j
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end
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### Driver code ###
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if __FILE__ == $0
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# Array containing duplicate elements
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nums = [1, 3, 6, 6, 6, 6, 6, 10, 12, 15]
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puts "\nArray nums = #{nums}"
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# Find the left and right boundaries using binary search
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for target in [6, 7]
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index = binary_search_left_edge(nums, target)
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puts "Index of the leftmost occurrence of #{target}: #{index}"
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index = binary_search_right_edge(nums, target)
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puts "Index of the rightmost occurrence of #{target}: #{index}"
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end
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end
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