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/**
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* File: hash_map_open_addressing.swift
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* Created Time: 2023-06-28
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* Author: nuomi1 (nuomi1@qq.com)
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*/
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import utils
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/* 开放寻址哈希表 */
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class HashMapOpenAddressing {
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var size: Int // 键值对数量
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var capacity: Int // 哈希表容量
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var loadThres: Double // 触发扩容的负载因子阈值
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var extendRatio: Int // 扩容倍数
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var buckets: [Pair?] // 桶数组
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var TOMBSTONE: Pair // 删除标记
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/* 构造方法 */
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init() {
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size = 0
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capacity = 4
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loadThres = 2.0 / 3.0
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extendRatio = 2
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buckets = Array(repeating: nil, count: capacity)
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TOMBSTONE = Pair(key: -1, val: "-1")
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}
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/* 哈希函数 */
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func hashFunc(key: Int) -> Int {
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key % capacity
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}
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/* 负载因子 */
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func loadFactor() -> Double {
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Double(size / capacity)
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}
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/* 搜索 key 对应的桶索引 */
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func findBucket(key: Int) -> Int {
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var index = hashFunc(key: key)
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var firstTombstone = -1
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// 线性探测,当遇到空桶时跳出
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while buckets[index] != nil {
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// 若遇到 key ,返回对应桶索引
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if buckets[index]!.key == key {
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// 若之前遇到了删除标记,则将键值对移动至该索引
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if firstTombstone != -1 {
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buckets[firstTombstone] = buckets[index]
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buckets[index] = TOMBSTONE
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return firstTombstone // 返回移动后的桶索引
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}
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return index // 返回桶索引
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}
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// 记录遇到的首个删除标记
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if firstTombstone == -1 && buckets[index] == TOMBSTONE {
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firstTombstone = index
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}
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// 计算桶索引,越过尾部返回头部
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index = (index + 1) % capacity
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}
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// 若 key 不存在,则返回添加点的索引
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return firstTombstone == -1 ? index : firstTombstone
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}
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/* 查询操作 */
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func get(key: Int) -> String? {
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// 搜索 key 对应的桶索引
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let index = findBucket(key: key)
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// 若找到键值对,则返回对应 val
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if buckets[index] != nil, buckets[index] != TOMBSTONE {
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return buckets[index]!.val
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}
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// 若键值对不存在,则返回 null
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return nil
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}
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/* 添加操作 */
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func put(key: Int, val: String) {
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// 当负载因子超过阈值时,执行扩容
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if loadFactor() > loadThres {
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extend()
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}
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// 搜索 key 对应的桶索引
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let index = findBucket(key: key)
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// 若找到键值对,则覆盖 val 并返回
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if buckets[index] != nil, buckets[index] != TOMBSTONE {
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buckets[index]!.val = val
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return
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}
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// 若键值对不存在,则添加该键值对
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buckets[index] = Pair(key: key, val: val)
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size += 1
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}
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/* 删除操作 */
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func remove(key: Int) {
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// 搜索 key 对应的桶索引
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let index = findBucket(key: key)
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// 若找到键值对,则用删除标记覆盖它
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if buckets[index] != nil, buckets[index] != TOMBSTONE {
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buckets[index] = TOMBSTONE
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size -= 1
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}
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}
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/* 扩容哈希表 */
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func extend() {
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// 暂存原哈希表
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let bucketsTmp = buckets
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// 初始化扩容后的新哈希表
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capacity *= extendRatio
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buckets = Array(repeating: nil, count: capacity)
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size = 0
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// 将键值对从原哈希表搬运至新哈希表
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for pair in bucketsTmp {
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if let pair, pair != TOMBSTONE {
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put(key: pair.key, val: pair.val)
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}
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}
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}
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/* 打印哈希表 */
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func print() {
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for pair in buckets {
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if pair == nil {
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Swift.print("null")
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} else if pair == TOMBSTONE {
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Swift.print("TOMBSTONE")
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} else {
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Swift.print("\(pair!.key) -> \(pair!.val)")
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}
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}
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}
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}
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@main
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enum _HashMapOpenAddressing {
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/* Driver Code */
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static func main() {
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/* 初始化哈希表 */
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let map = HashMapOpenAddressing()
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/* 添加操作 */
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// 在哈希表中添加键值对 (key, value)
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map.put(key: 12836, val: "小哈")
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map.put(key: 15937, val: "小啰")
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map.put(key: 16750, val: "小算")
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map.put(key: 13276, val: "小法")
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map.put(key: 10583, val: "小鸭")
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print("\n添加完成后,哈希表为\nKey -> Value")
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map.print()
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/* 查询操作 */
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// 向哈希表输入键 key ,得到值 value
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let name = map.get(key: 13276)
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print("\n输入学号 13276 ,查询到姓名 \(name!)")
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/* 删除操作 */
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// 在哈希表中删除键值对 (key, value)
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map.remove(key: 16750)
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print("\n删除 16750 后,哈希表为\nKey -> Value")
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map.print()
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}
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}
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