66 lines
2.3 KiB
Rust
66 lines
2.3 KiB
Rust
/*
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* File: binary_search.rs
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* Created Time: 2023-02-05
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* Author: codingonion (coderonion@gmail.com)
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*/
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/* Binary search (double closed interval) */
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fn binary_search(nums: &[i32], target: i32) -> i32 {
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// Initialize double closed interval [0, n-1], i.e., i, j point to the first element and last element of the array respectively
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let mut i = 0;
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let mut j = nums.len() as i32 - 1;
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// Loop until the search interval is empty (when i > j, it is empty)
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while i <= j {
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let m = i + (j - i) / 2; // Calculate midpoint index m
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if nums[m as usize] < target {
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// This situation indicates that target is in the interval [m+1, j]
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i = m + 1;
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} else if nums[m as usize] > target {
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// This situation indicates that target is in the interval [i, m-1]
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j = m - 1;
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} else {
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// Found the target element, thus return its index
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return m;
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}
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}
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// Did not find the target element, thus return -1
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return -1;
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}
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/* Binary search (left closed right open interval) */
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fn binary_search_lcro(nums: &[i32], target: i32) -> i32 {
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// Initialize left closed right open interval [0, n), i.e., i, j point to the first element and the last element +1 of the array respectively
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let mut i = 0;
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let mut j = nums.len() as i32;
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// Loop until the search interval is empty (when i = j, it is empty)
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while i < j {
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let m = i + (j - i) / 2; // Calculate midpoint index m
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if nums[m as usize] < target {
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// This situation indicates that target is in the interval [m+1, j)
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i = m + 1;
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} else if nums[m as usize] > target {
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// This situation indicates that target is in the interval [i, m)
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j = m;
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} else {
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// Found the target element, thus return its index
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return m;
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}
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}
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// Did not find the target element, thus return -1
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return -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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// Binary search (double closed interval)
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let mut index = binary_search(&nums, target);
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println!("The index of target element 6 is {index}");
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// Binary search (left closed right open interval)
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index = binary_search_lcro(&nums, target);
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println!("The index of target element 6 is {index}");
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}
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