mirror of
https://github.com/TheAlgorithms/Ruby
synced 2025-01-16 03:43:19 +01:00
43 lines
1.6 KiB
Ruby
43 lines
1.6 KiB
Ruby
=begin
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Ternary Search
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-------------------------------
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Ternary search is a searching technique that is used to search the position of a specific value in an array.
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Ternary search is a divide-and-conquer algorithm.
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It is mandatory for the array to be sorted (in which you will search for an element).
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The array is divided into three parts and then we determine in which part the element exists.
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In this search, after each iteration it neglects 1/3 part of the array and repeats the same operations on the remaining ⅔.
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Time Complexity: O(log3 n)
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Space Complexity: O(1)
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=end
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def ternary_search(l, r, key, arr)
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#l is the starting index and r is the ending index of the array/sub-array.
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if (r >= l)
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#find mid1 and mid2
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mid1 = l + (r - l) / 3
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mid2 = r - (r - l) / 3
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#check if key is equal to mid1
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if arr[mid1] == key
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mid1
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#check if key is equal to mid2
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elsif arr[mid2] == key
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mid2
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#Since key is not present at mid, check in which region it is present
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#then repeat the Search operation in that region
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elsif key < arr[mid1]
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ternary_search(l, mid1 - 1, key, arr)
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elsif (key > arr[mid2])
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ternary_search(mid2 + 1, r, key, arr)
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else
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ternary_search(mid1 + 1, mid2 - 1, key, arr)
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end
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end
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end
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puts "Enter a space-separated list:"
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arr = gets.chomp.split(' ').map(&:to_i)
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puts "Enter a value to be searched:"
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key = gets.chomp.to_i
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puts ternary_search(0, arr.length - 1, key, arr) != nil ?
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"Found at index #{ternary_search(0, arr.length - 1, key, arr)}" :
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"Not found"
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