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43 lines
931 B
43 lines
931 B
6 months ago
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=begin
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File: binary_search_recur.rb
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Created Time: 2024-05-13
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Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
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=end
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### 二分查找：问题 f(i, j) ###
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def dfs(nums, target, i, j)
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# 若区间为空，代表无目标元素，则返回 -1
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return -1 if i > j
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# 计算中点索引 m
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m = (i + j) / 2
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if nums[m] < target
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# 递归子问题 f(m+1, j)
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return dfs(nums, target, m + 1, j)
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elsif nums[m] > target
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# 递归子问题 f(i, m-1)
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return dfs(nums, target, i, m - 1)
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else
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# 找到目标元素，返回其索引
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return m
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end
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end
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### 二分查找 ###
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def binary_search(nums, target)
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n = nums.length
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# 求解问题 f(0, n-1)
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dfs(nums, target, 0, n - 1)
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end
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### Driver Code ###
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if __FILE__ == $0
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target = 6
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nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35]
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# 二分查找（双闭区间）
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index = binary_search(nums, target)
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puts "目标元素 6 的索引 = #{index}"
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end
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