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59 lines
1.9 KiB
59 lines
1.9 KiB
/*
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* File: binary_search_edge.rs
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* Created Time: 2023-05-31
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* Author: WSL0809 (wslzzy@outlook.com)
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*/
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/* 二分查找最左一个元素 */
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fn binary_search_left_edge(nums: &[i32], target: i32) -> i32 {
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let mut i = 0;
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let mut j = nums.len() as i32 - 1; // 初始化双闭区间 [0, n-1]
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while i <= j {
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let m = i + (j - i) / 2; // 计算中点索引 m
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if nums[m as usize] < target {
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i = m + 1; // target 在区间 [m+1, j] 中
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} else if nums[m as usize] > target {
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j = m - 1; // target 在区间 [i, m-1] 中
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} else {
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j = m - 1; // 首个小于 target 的元素在区间 [i, m-1] 中
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}
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}
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if i == nums.len() as i32 || nums[i as usize] != target {
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return -1; // 未找到目标元素，返回 -1
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}
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i
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}
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/* 二分查找最右一个元素 */
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fn binary_search_right_edge(nums: &[i32], target: i32) -> i32 {
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let mut i = 0;
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let mut j = nums.len() as i32 - 1; // 初始化双闭区间 [0, n-1]
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while i <= j {
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let m = i + (j - i) / 2; // 计算中点索引 m
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if nums[m as usize] < target {
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i = m + 1; // target 在区间 [m+1, j] 中
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} else if nums[m as usize] > target {
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j = m - 1; // target 在区间 [i, m-1] 中
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} else {
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i = m + 1; // 首个大于 target 的元素在区间 [m+1, j] 中
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}
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}
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if j < 0 || nums[j as usize] != target {
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return -1; // 未找到目标元素，返回 -1
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}
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j
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}
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/* Driver Code */
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pub fn main() {
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let target = 6;
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let nums = [1, 3, 6, 6, 6, 6, 6, 10, 12, 15];
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// 二分查找最左一个元素
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let index_left = binary_search_left_edge(&nums, target);
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println!("数组中最左一个元素 6 的索引 = {}", index_left);
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// 二分查找最右一个元素
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let index_right = binary_search_right_edge(&nums, target);
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println!("数组中最右一个元素 6 的索引 = {}", index_right);
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} |