Add kotlin code for the chapter of hashing (#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
2026-08-16 13:40:58 +00:00 · 2024-03-12 14:08:15 +08:00
parent cf0817370b
commit eadf4c86d4
6 changed files with 579 additions and 0 deletions
@@ -0,0 +1,145 @@
+/**
+ * File: hash_map_chaining.kt
+ * Created Time: 2024-01-25
+ * Author: curtishd (1023632660@qq.com)
+ */
+
+package chapter_hashing
+
+/* 链式地址哈希表 */
+class HashMapChaining() {
+    var size: Int // 键值对数量
+    var capacity: Int // 哈希表容量
+    val loadThres: Double // 触发扩容的负载因子阈值
+    val extendRatio: Int // 扩容倍数
+    var buckets: MutableList<MutableList<Pair>> // 桶数组
+
+    /* 构造方法 */
+    init {
+        size = 0
+        capacity = 4
+        loadThres = 2.0 / 3.0
+        extendRatio = 2
+        buckets = ArrayList(capacity)
+        for (i in 0..<capacity) {
+            buckets.add(mutableListOf())
+        }
+    }
+
+    /* 哈希函数 */
+    fun hashFunc(key: Int): Int {
+        return key % capacity
+    }
+
+    /* 负载因子 */
+    fun loadFactor(): Double {
+        return (size / capacity).toDouble()
+    }
+
+    /* 查询操作 */
+    fun get(key: Int): String? {
+        val index = hashFunc(key)
+        val bucket = buckets[index]
+        // 遍历桶，若找到 key ，则返回对应 val
+        for (pair in bucket) {
+            if (pair.key == key) return pair.value
+        }
+        // 若未找到 key ，则返回 null
+        return null
+    }
+
+    /* 添加操作 */
+    fun put(key: Int, value: String) {
+        // 当负载因子超过阈值时，执行扩容
+        if (loadFactor() > loadThres) {
+            extend()
+        }
+        val index = hashFunc(key)
+        val bucket = buckets[index]
+        // 遍历桶，若遇到指定 key ，则更新对应 val 并返回
+        for (pair in bucket) {
+            if (pair.key == key) {
+                pair.value = value
+                return
+            }
+        }
+        // 若无该 key ，则将键值对添加至尾部
+        val pair = Pair(key, value)
+        bucket.add(pair)
+        size++
+    }
+
+    /* 删除操作 */
+    fun remove(key: Int) {
+        val index = hashFunc(key)
+        val bucket = buckets[index]
+        // 遍历桶，从中删除键值对
+        for (pair in bucket) {
+            if (pair.key == key) {
+                bucket.remove(pair)
+                size--
+                break
+            }
+        }
+    }
+
+    /* 扩容哈希表 */
+    fun extend() {
+        // 暂存原哈希表
+        val bucketsTmp = buckets
+        // 初始化扩容后的新哈希表
+        capacity *= extendRatio
+        // mutablelist 无固定大小
+        buckets = mutableListOf()
+        for (i in 0..<capacity) {
+            buckets.add(mutableListOf())
+        }
+        size = 0
+        // 将键值对从原哈希表搬运至新哈希表
+        for (bucket in bucketsTmp) {
+            for (pair in bucket) {
+                put(pair.key, pair.value)
+            }
+        }
+    }
+
+    /* 打印哈希表 */
+    fun print() {
+        for (bucket in buckets) {
+            val res = mutableListOf<String>()
+            for (pair in bucket) {
+                val k = pair.key
+                val v = pair.value
+                res.add("$k -> $v")
+            }
+            println(res)
+        }
+    }
+}
+
+/* Driver Code */
+fun main() {
+    /* 初始化哈希表 */
+    val map = HashMapChaining()
+
+    /* 添加操作 */
+    // 在哈希表中添加键值对 (key, value)
+    map.put(12836, "小哈")
+    map.put(15937, "小啰")
+    map.put(16750, "小算")
+    map.put(13276, "小法")
+    map.put(10583, "小鸭")
+    println("\n添加完成后，哈希表为\nKey -> Value")
+    map.print()
+
+    /* 查询操作 */
+    // 向哈希表中输入键 key ，得到值 value
+    val name = map.get(13276)
+    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)
+    map.remove(12836)
+    println("\n删除 12836 后，哈希表为\nKey -> Value")
+    map.print()
+}