rust——二分查找法

Posted 2021-07-02 码功驿站

实现一：循环

fn search<E: PartialOrd>(data: Vec<E>, target: E) -> i32 { let mut l: i32 = 0; // 左闭右开区间 let mut r = data.len() as i32; while l < r { let mid = l + (r - l) / 2; if data[mid as usize] == target { return mid; } if data[mid as usize] < target { l = mid + 1; } else { r = mid } } return -1;}

实现二：递归

// 二分查找fn search<E: PartialOrd>(data: Vec<E>, target: E) -> i32 { recursion_search(&data, 0, data.len() as i32 - 1, target)}
// 递归调用fn recursion_search<E: PartialOrd>(data: &Vec<E>, l: i32, r: i32, target: E) -> i32 { if l > r { return -1; } // 避免溢出 let mid = l + (r - l) / 2; if data[mid as usize] == target { return mid; } if data[mid as usize] < target { // 中间值小于目标，就在右边寻找 recursion_search(data, mid + 1, r, target) } else { // 中间值大于目标，就在左边寻找 // mid - 1，如果mid=0，-1使用usize就会溢出，所以参数使用i32 recursion_search(data, l, mid - 1, target) }}
#[cfg(test)]mod tests { use crate::binary_search::search;
 #[test] fn it_works() { let data = vec![5]; assert_eq!(search(data, -5), -1); }}