You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
43 lines
931 B
43 lines
931 B
=begin
|
|
File: binary_search_recur.rb
|
|
Created Time: 2024-05-13
|
|
Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
|
|
=end
|
|
|
|
### 二分查找：问题 f(i, j) ###
|
|
def dfs(nums, target, i, j)
|
|
# 若区间为空，代表无目标元素，则返回 -1
|
|
return -1 if i > j
|
|
|
|
# 计算中点索引 m
|
|
m = (i + j) / 2
|
|
|
|
if nums[m] < target
|
|
# 递归子问题 f(m+1, j)
|
|
return dfs(nums, target, m + 1, j)
|
|
elsif nums[m] > target
|
|
# 递归子问题 f(i, m-1)
|
|
return dfs(nums, target, i, m - 1)
|
|
else
|
|
# 找到目标元素，返回其索引
|
|
return m
|
|
end
|
|
end
|
|
|
|
### 二分查找 ###
|
|
def binary_search(nums, target)
|
|
n = nums.length
|
|
# 求解问题 f(0, n-1)
|
|
dfs(nums, target, 0, n - 1)
|
|
end
|
|
|
|
### Driver Code ###
|
|
if __FILE__ == $0
|
|
target = 6
|
|
nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35]
|
|
|
|
# 二分查找（双闭区间）
|
|
index = binary_search(nums, target)
|
|
puts "目标元素 6 的索引 = #{index}"
|
|
end
|