mirror of
https://github.com/krahets/hello-algo.git
synced 2024-12-26 21:06:29 +08:00
d484b08c15
* Update bucket_sort.c * Fix the comments in quick_sort.c * Update the announce badge * Sync zh and zh-hant versions * Update contributors list. * Sync zh and zh-hant versions. * Sync zh and zh-hant versions. * Update the contributors list * Update the version number
47 lines
1.2 KiB
Ruby
47 lines
1.2 KiB
Ruby
=begin
|
||
File: binary_search_edge.rb
|
||
Created Time: 2024-04-09
|
||
Author: Blue Bean (lonnnnnnner@gmail.com)
|
||
=end
|
||
|
||
require_relative './binary_search_insertion'
|
||
|
||
### 二分搜尋最左一個 target ###
|
||
def binary_search_left_edge(nums, target)
|
||
# 等價於查詢 target 的插入點
|
||
i = binary_search_insertion(nums, target)
|
||
|
||
# 未找到 target ，返回 -1
|
||
return -1 if i == nums.length || nums[i] != target
|
||
|
||
i # 找到 target ，返回索引 i
|
||
end
|
||
|
||
### 二分搜尋最右一個 target ###
|
||
def binary_search_right_edge(nums, target)
|
||
# 轉化為查詢最左一個 target + 1
|
||
i = binary_search_insertion(nums, target + 1)
|
||
|
||
# j 指向最右一個 target ，i 指向首個大於 target 的元素
|
||
j = i - 1
|
||
|
||
# 未找到 target ，返回 -1
|
||
return -1 if j == -1 || nums[j] != target
|
||
|
||
j # 找到 target ，返回索引 j
|
||
end
|
||
|
||
### Driver Code ###
|
||
if __FILE__ == $0
|
||
# 包含重複元素的陣列
|
||
nums = [1, 3, 6, 6, 6, 6, 6, 10, 12, 15]
|
||
puts "\n陣列 nums = #{nums}"
|
||
|
||
# 二分搜尋左邊界和右邊界
|
||
for target in [6, 7]
|
||
index = binary_search_left_edge(nums, target)
|
||
puts "最左一個元素 #{target} 的索引為 #{index}"
|
||
index = binary_search_right_edge(nums, target)
|
||
puts "最右一個元素 #{target} 的索引為 #{index}"
|
||
end
|
||
end
|