diff --git a/codes/rust/chapter_hashing/array_hash_map.rs b/codes/rust/chapter_hashing/array_hash_map.rs index b77b5a68..3216509b 100644 --- a/codes/rust/chapter_hashing/array_hash_map.rs +++ b/codes/rust/chapter_hashing/array_hash_map.rs @@ -4,13 +4,12 @@ * Author: xBLACICEx (xBLACKICEx@outlook.com) */ -#[derive(Debug, Clone)] /* 键值对 */ +#[derive(Debug, Clone, PartialEq)] pub struct Pair { pub key: i32, pub val: String, } - /* 基于数组简易实现的哈希表 */ pub struct ArrayHashMap { buckets: Vec> diff --git a/codes/rust/chapter_hashing/hash_map_open_addressing.rs b/codes/rust/chapter_hashing/hash_map_open_addressing.rs index 0be96e61..e9b9f025 100644 --- a/codes/rust/chapter_hashing/hash_map_open_addressing.rs +++ b/codes/rust/chapter_hashing/hash_map_open_addressing.rs @@ -1,24 +1,23 @@ /* * File: hash_map_open_addressing.rs * Created Time: 2023-07-16 - * Author: WSL0809 (wslzzy@outlook.com) + * Author: WSL0809 (wslzzy@outlook.com), night-cruise (2586447362@qq.com) */ +#![allow(non_snake_case)] +#![allow(unused)] -#[derive(Clone, PartialEq)] -/* 键值对 */ -struct Pair { - key: i32, - val: String, -} +mod array_hash_map; + +use array_hash_map::Pair; /* 开放寻址哈希表 */ struct HashMapOpenAddressing { - size: usize, - capacity: usize, - load_thres: f32, - extend_ratio: usize, - buckets: Vec>, - removed: Pair, + size: usize, // 键值对数量 + capacity: usize, // 哈希表容量 + load_thres: f64, // 触发扩容的负载因子阈值 + extend_ratio: usize, // 扩容倍数 + buckets: Vec>, // 桶数组 + TOMBSTONE: Option, // 删除标记 } @@ -31,10 +30,7 @@ impl HashMapOpenAddressing { load_thres: 2.0 / 3.0, extend_ratio: 2, buckets: vec![None; 4], - removed: Pair { - key: -1, - val: "-1".to_string(), - }, + TOMBSTONE: Some(Pair {key: -1, val: "-1".to_string()}), } } @@ -44,27 +40,46 @@ impl HashMapOpenAddressing { } /* 负载因子 */ - fn load_factor(&self) -> f32 { - self.size as f32 / self.capacity as f32 + fn load_factor(&self) -> f64 { + self.size as f64 / self.capacity as f64 + } + + /* 搜索 key 对应的桶索引 */ + fn find_bucket(&mut self, key: i32) -> usize { + let mut index = self.hash_func(key); + let mut first_tombstone = -1; + // 线性探测，当遇到空桶时跳出 + while self.buckets[index].is_some() { + // 若遇到 key，返回对应的桶索引 + if self.buckets[index].as_ref().unwrap().key == key { + // 若之前遇到了删除标记，则将建值对移动至该索引 + if first_tombstone != -1 { + self.buckets[first_tombstone as usize] = self.buckets[index].take(); + self.buckets[index] = self.TOMBSTONE.clone(); + return first_tombstone as usize; // 返回移动后的桶索引 + } + return index; // 返回桶索引 + } + // 记录遇到的首个删除标记 + if first_tombstone == -1 && self.buckets[index] == self.TOMBSTONE { + first_tombstone = index as i32; + } + // 计算桶索引，越过尾部返回头部 + index = (index + 1) % self.capacity; + } + // 若 key 不存在，则返回添加点的索引 + if first_tombstone == -1 { index } else { first_tombstone as usize } } /* 查询操作 */ - fn get(&self, key: i32) -> Option<&str> { - let mut index = self.hash_func(key); - let capacity = self.capacity; - // 线性探测，从 index 开始向后遍历 - for _ in 0..capacity { - // 计算桶索引，越过尾部返回头部 - let j = (index + 1) % capacity; - match &self.buckets[j] { - // 若遇到空桶，说明无此 key ，则返回 None - None => return None, - // 若遇到指定 key ，则返回对应 val - Some(pair) if pair.key == key && pair != &self.removed => return Some(&pair.val), - _ => index = j, - } + fn get(&mut self, key: i32) -> Option<&str> { + // 搜索 key 对应的桶索引 + let index = self.find_bucket(key); + // 若找到键值对，则返回对应 val + if self.buckets[index].is_some() && self.buckets[index] != self.TOMBSTONE { + return self.buckets[index].as_ref().map(|pair| &pair.val as &str); } - + // 若键值对不存在，则返回 null None } @@ -74,57 +89,29 @@ impl HashMapOpenAddressing { if self.load_factor() > self.load_thres { self.extend(); } - - let mut index = self.hash_func(key); - let capacity = self.capacity; - - // 线性探测，从 index 开始向后遍历 - for _ in 0..capacity { - //计算桶索引，越过尾部返回头部 - let j = (index + 1) % capacity; - // 若遇到空桶、或带有删除标记的桶，则将键值对放入该桶 - match &mut self.buckets[j] { - bucket @ &mut None | bucket @ &mut Some(Pair { key: -1, .. }) => { - *bucket = Some(Pair { key, val }); - self.size += 1; - return; - } - // 若遇到指定 key ，则更新对应 val - Some(pair) if pair.key == key => { - pair.val = val; - return; - } - _ => index = j, - } + // 搜索 key 对应的桶索引 + let index = self.find_bucket(key); + // 若找到键值对，则覆盖 val 并返回 + if self.buckets[index].is_some() && self.buckets[index] != self.TOMBSTONE { + self.buckets[index].as_mut().unwrap().val = val; + return; } + // 若键值对不存在，则添加该键值对 + self.buckets[index] = Some(Pair { key, val }); + self.size += 1; } /* 删除操作 */ fn remove(&mut self, key: i32) { - let mut index = self.hash_func(key); - let capacity = self.capacity; - - // 遍历桶，从中删除键值对 - for _ in 0..capacity { - let j = (index + 1) % capacity; - match &mut self.buckets[j] { - // 若遇到空桶，说明无此 key ，则直接返回 - None => return, - // 若遇到指定 key ，则标记删除并返回 - Some(pair) if pair.key == key => { - *pair = Pair { - key: -1, - val: "-1".to_string(), - }; - self.size -= 1; - return; - } - _ => index = j, - } + // 搜索 key 对应的桶索引 + let index = self.find_bucket(key); + // 若找到键值对，则用删除标记覆盖它 + if self.buckets[index].is_some() && self.buckets[index] != self.TOMBSTONE { + self.buckets[index] = self.TOMBSTONE.clone(); + self.size -= 1; } } - /* 扩容哈希表 */ fn extend(&mut self) { // 暂存原哈希表 @@ -136,17 +123,24 @@ impl HashMapOpenAddressing { // 将键值对从原哈希表搬运至新哈希表 for pair in buckets_tmp { - if let Some(pair) = pair { - self.put(pair.key, pair.val); + if pair.is_none() || pair == self.TOMBSTONE { + continue; } + let pair = pair.unwrap(); + + self.put(pair.key, pair.val); } } /* 打印哈希表 */ fn print(&self) { for pair in &self.buckets { - match pair { - Some(pair) => println!("{} -> {}", pair.key, pair.val), - None => println!("None"), + if pair.is_none() { + println!("null"); + } else if pair == &self.TOMBSTONE { + println!("TOMBSTONE"); + } else { + let pair = pair.as_ref().unwrap(); + println!("{} -> {}", pair.key, pair.val); } } } @@ -165,17 +159,17 @@ fn main() { hashmap.put(13276, "小法".to_string()); hashmap.put(10583, "小鸭".to_string()); - println!("\n添加完成后,哈希表为\nKey -> Value"); + println!("\n添加完成后，哈希表为\nKey -> Value"); hashmap.print(); /* 查询操作 */ - // 向哈希表输入键 key ，得到值 value + // 向哈希表输入键 key ，得到值 val let name = hashmap.get(13276).unwrap(); - println!("\n输入学号 13276 ,查询到姓名 {}", name); + println!("\n输入学号 13276 ，查询到姓名 {}", name); /* 删除操作 */ - // 在哈希表中删除键值对 (key, value) + // 在哈希表中删除键值对 (key, val) hashmap.remove(16750); - println!("\n删除 16750 后,哈希表为\nKey -> Value"); + println!("\n删除 16750 后，哈希表为\nKey -> Value"); hashmap.print(); }