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/*
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* File: binary_search_edge.rs
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* Created Time: 2023-08-30
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* Author: night-cruise (2586447362@qq.com)
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*/
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mod binary_search_insertion;
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use binary_search_insertion::binary_search_insertion;
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/* 二分搜尋最左一個 target */
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fn binary_search_left_edge(nums: &[i32], target: i32) -> i32 {
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// 等價於查詢 target 的插入點
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let i = binary_search_insertion(nums, target);
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// 未找到 target ，返回 -1
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if i == nums.len() as i32 || nums[i as usize] != target {
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return -1;
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}
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// 找到 target ，返回索引 i
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i
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}
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/* 二分搜尋最右一個 target */
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fn binary_search_right_edge(nums: &[i32], target: i32) -> i32 {
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// 轉化為查詢最左一個 target + 1
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let i = binary_search_insertion(nums, target + 1);
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// j 指向最右一個 target ，i 指向首個大於 target 的元素
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let j = i - 1;
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// 未找到 target ，返回 -1
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if j == -1 || nums[j as usize] != target {
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return -1;
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}
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// 找到 target ，返回索引 j
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j
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}
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/* Driver Code */
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fn main() {
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// 包含重複元素的陣列
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let nums = [1, 3, 6, 6, 6, 6, 6, 10, 12, 15];
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println!("\n陣列 nums = {:?}", nums);
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// 二分搜尋左邊界和右邊界
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for target in [6, 7] {
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let index = binary_search_left_edge(&nums, target);
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println!("最左一個元素 {} 的索引為 {}", target, index);
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let index = binary_search_right_edge(&nums, target);
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println!("最右一個元素 {} 的索引為 {}", target, index);
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}
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}
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