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Add kotlin code for the chapter of hashing (krahets#1104)
* feat(kotlin): add kotlin code for dynamic programming. * Update knapsack.kt * feat(kotlin): add kotlin codes for graph. * style(kotlin): reformatted the codes. * feat(kotlin): add kotlin codes for the chapter of greedy. * Update max_product_cutting.kt * feat(kotlin): add kotlin code for chapter of hashing. * style(kotlin): modified some comment * Update array_hash_map.kt * Update hash_map_chaining.kt * Update hash_map_chaining.kt
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‎codes/kotlin/chapter_hashing/array_hash_map.kt‎

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/**
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* File: array_hash_map.kt
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* Created Time: 2024-01-25
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* Author: curtishd ([email protected])
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*/
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package chapter_hashing
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/* 键值对 */
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class Pair(
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var key: Int,
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var value: String
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)
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/* 基于数组实现的哈希表 */
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class ArrayHashMap {
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private val buckets = arrayOfNulls<Pair>(100)
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/* 构造方法 */
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init {
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// 初始化数组，包含 100 个桶
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for (i in 0..<100) {
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buckets[i] = null
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}
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}
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/* 哈希函数 */
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fun hashFunc(key: Int): Int {
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val index = key % 100
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return index
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}
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/* 查询操作 */
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fun get(key: Int): String? {
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val index = hashFunc(key)
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val pair = buckets[index] ?: return null
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return pair.value
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}
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/* 添加操作 */
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fun put(key: Int, value: String) {
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val pair = Pair(key, value)
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val index = hashFunc(key)
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buckets[index] = pair
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}
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/* 删除操作 */
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fun remove(key: Int) {
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val index = hashFunc(key)
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// 置为 null ，代表删除
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buckets[index] = null
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}
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/* 获取所有键值对 */
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fun pairSet(): MutableList<Pair> {
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val pairSet = ArrayList<Pair>()
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for (pair in buckets) {
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if (pair != null) pairSet.add(pair)
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}
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return pairSet
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}
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/* 获取所有键 */
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fun keySet(): MutableList<Int> {
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val keySet = ArrayList<Int>()
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for (pair in buckets) {
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if (pair != null) keySet.add(pair.key)
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}
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return keySet
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}
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/* 获取所有值 */
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fun valueSet(): MutableList<String> {
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val valueSet = ArrayList<String>()
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for (pair in buckets) {
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pair?.let { valueSet.add(it.value) }
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}
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return valueSet
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}
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/* 打印哈希表 */
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fun print() {
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for (kv in pairSet()) {
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val key = kv.key
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val value = kv.value
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println("${key}->${value}")
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}
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}
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}
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/* Driver Code */
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fun main() {
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/* 初始化哈希表 */
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val map = ArrayHashMap()
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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(12836, "小哈")
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map.put(15937, "小啰")
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map.put(16750, "小算")
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map.put(13276, "小法")
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map.put(10583, "小鸭")
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println("\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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// 向哈希表中输入键 key ，得到值 value
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val name: String? = map.get(15937)
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println("\n输入学号 15937 ，查询到姓名 $name")
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/* 删除操作 */
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// 在哈希表中删除键值对 (key, value)
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map.remove(10583)
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println("\n删除 10583 后，哈希表为\nKey -> Value")
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map.print()
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/* 遍历哈希表 */
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println("\n遍历键值对 Key->Value")
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for (kv in map.pairSet()) {
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println("${kv.key} -> ${kv.value}")
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}
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println("\n单独遍历键 Key")
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for (key in map.keySet()) {
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println(key)
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}
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println("\n单独遍历值 Value")
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for (value in map.valueSet()) {
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println(value)
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}
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}

‎codes/kotlin/chapter_hashing/built_in_hash.kt‎

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/**
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* File: built_in_hash.kt
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* Created Time: 2024-01-25
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* Author: curtishd ([email protected])
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*/
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package chapter_hashing
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import utils.ListNode
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/* Driver Code */
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fun main() {
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val num = 3
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val hashNum = Integer.hashCode(num)
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println("整数 $num 的哈希值为 $hashNum")
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val bol = true
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val hashBol = Boolean.hashCode()
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println("布尔量 $bol 的哈希值为 $hashBol")
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val dec = 3.14159
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val hashDec = java.lang.Double.hashCode(dec)
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println("小数 $dec 的哈希值为 $hashDec")
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val str = "Hello 算法"
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val hashStr = str.hashCode()
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println("字符串 $str 的哈希值为 $hashStr")
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val arr = arrayOf<Any>(12836, "小哈")
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val hashTup = arr.contentHashCode()
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println("数组 ${arr.contentToString()} 的哈希值为 ${hashTup}")
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val obj = ListNode(0)
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val hashObj = obj.hashCode()
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println("节点对象 $obj 的哈希值为 $hashObj")
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}

‎codes/kotlin/chapter_hashing/hash_map.kt‎

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/**
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* File: hash_map.kt
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* Created Time: 2024-01-25
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* Author: curtishd ([email protected])
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*/
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package chapter_hashing
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import utils.printHashMap
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/* Driver Code */
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fun main() {
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/* 初始化哈希表 */
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val map: MutableMap<Int, String> = HashMap()
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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[12836] = "小哈"
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map[15937] = "小啰"
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map[16750] = "小算"
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map[13276] = "小法"
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map[10583] = "小鸭"
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println("\n添加完成后，哈希表为\nKey -> Value")
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printHashMap(map)
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/* 查询操作 */
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// 向哈希表中输入键 key ，得到值 value
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val name = map[15937]
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println("\n输入学号 15937 ，查询到姓名 $name")
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/* 删除操作 */
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// 在哈希表中删除键值对 (key, value)
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map.remove(10583)
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println("\n删除 10583 后，哈希表为\nKey -> Value")
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printHashMap(map)
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/* 遍历哈希表 */
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println("\n遍历键值对 Key->Value")
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for ((key, value) in map) {
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println("$key -> $value")
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}
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println("\n单独遍历键 Key")
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for (key in map.keys) {
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println(key)
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}
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println("\n单独遍历值 Value")
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for (value in map.values) {
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println(value)
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}
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}

‎codes/kotlin/chapter_hashing/hash_map_chaining.kt‎

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/**
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* File: hash_map_chaining.kt
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* Created Time: 2024-01-25
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* Author: curtishd ([email protected])
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*/
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package chapter_hashing
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/* 链式地址哈希表 */
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class HashMapChaining() {
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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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val loadThres: Double // 触发扩容的负载因子阈值
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val extendRatio: Int // 扩容倍数
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var buckets: MutableList<MutableList<Pair>> // 桶数组
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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 = ArrayList(capacity)
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for (i in 0..<capacity) {
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buckets.add(mutableListOf())
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}
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}
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/* 哈希函数 */
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fun hashFunc(key: Int): Int {
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return key % capacity
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}
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/* 负载因子 */
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fun loadFactor(): Double {
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return (size / capacity).toDouble()
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}
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/* 查询操作 */
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fun get(key: Int): String? {
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val index = hashFunc(key)
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val bucket = buckets[index]
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// 遍历桶，若找到 key ，则返回对应 val
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for (pair in bucket) {
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if (pair.key == key) return pair.value
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}
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// 若未找到 key ，则返回 null
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return null
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}
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/* 添加操作 */
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fun put(key: Int, value: 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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val index = hashFunc(key)
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val bucket = buckets[index]
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// 遍历桶，若遇到指定 key ，则更新对应 val 并返回
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for (pair in bucket) {
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if (pair.key == key) {
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pair.value = value
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return
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}
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}
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// 若无该 key ，则将键值对添加至尾部
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val pair = Pair(key, value)
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bucket.add(pair)
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size++
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}
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/* 删除操作 */
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fun remove(key: Int) {
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val index = hashFunc(key)
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val bucket = buckets[index]
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// 遍历桶，从中删除键值对
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for (pair in bucket) {
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if (pair.key == key) {
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bucket.remove(pair)
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size--
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break
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}
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}
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}
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/* 扩容哈希表 */
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fun extend() {
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// 暂存原哈希表
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val 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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// mutablelist 无固定大小
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buckets = mutableListOf()
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for (i in 0..<capacity) {
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buckets.add(mutableListOf())
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}
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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 (bucket in bucketsTmp) {
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for (pair in bucket) {
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put(pair.key, pair.value)
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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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fun print() {
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for (bucket in buckets) {
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val res = mutableListOf<String>()
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for (pair in bucket) {
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val k = pair.key
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val v = pair.value
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res.add("$k -> $v")
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}
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println(res)
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}
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}
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}
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/* Driver Code */
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fun main() {
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/* 初始化哈希表 */
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val map = HashMapChaining()
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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(12836, "小哈")
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map.put(15937, "小啰")
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map.put(16750, "小算")
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map.put(13276, "小法")
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map.put(10583, "小鸭")
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println("\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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// 向哈希表中输入键 key ，得到值 value
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val name = map.get(13276)
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println("\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(12836)
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println("\n删除 12836 后，哈希表为\nKey -> Value")
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map.print()
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}

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