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40 lines
1.0 KiB
40 lines
1.0 KiB
/*
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* File: binary_search_recur.rs
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* Created Time: 2023-07-15
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* Author: sjinzh (sjinzh@gmail.com)
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*/
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/* 二分查找：问题 f(i, j) */
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fn dfs(nums: &[i32], target: i32, i: i32, j: i32) -> i32 {
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// 若区间为空，代表无目标元素，则返回 -1
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if i > j { return -1; }
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let m: i32 = (i + j) / 2;
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if nums[m as usize] < 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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} else if nums[m as usize] > 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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}
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}
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/* 二分查找 */
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fn binary_search(nums: &[i32], target: i32) -> i32 {
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let n = nums.len() as i32;
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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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}
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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, 8, 12, 15, 23, 26, 31, 35 ];
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// 二分查找（双闭区间）
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let index = binary_search(&nums, target);
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println!("目标元素 6 的索引 = {index}");
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}
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