feat(chapter_hashing): Add js and ts codes for chapter hashing

codes/javascript/chapter_hashing/array_hash_map.js

@@ -62,7 +62,7 @@ class ArrayHashMap {
         let arr = [];
         for (let i = 0; i < this.#buckets.length; i++) {
             if (this.#buckets[i]) {
-                arr.push(this.#buckets[i]?.key);
+                arr.push(this.#buckets[i].key);
             }
         }
         return arr;
@@ -73,7 +73,7 @@ class ArrayHashMap {
         let arr = [];
         for (let i = 0; i < this.#buckets.length; i++) {
             if (this.#buckets[i]) {
-                arr.push(this.#buckets[i]?.val);
+                arr.push(this.#buckets[i].val);
             }
         }
         return arr;

codes/javascript/chapter_hashing/hash_map_chaining.js

@@ -0,0 +1,142 @@
+/**
+ * File: hash_map_chaining.js
+ * Created Time: 2023-08-06
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* 键值对 Number -> String */
+class Pair {
+    constructor(key, val) {
+        this.key = key;
+        this.val = val;
+    }
+}
+
+/* 链式地址哈希表 */
+class HashMapChaining {
+    #size; // 键值对数量
+    #capacity; // 哈希表容量
+    #loadThres; // 触发扩容的负载因子阈值
+    #extendRatio; // 扩容倍数
+    #buckets; // 桶数组
+
+    /* 构造方法 */
+    constructor() {
+        this.#size = 0;
+        this.#capacity = 4;
+        this.#loadThres = 2 / 3.0;
+        this.#extendRatio = 2;
+        this.#buckets = new Array(this.#capacity).fill(null).map((x) => []);
+    }
+
+    /* 哈希函数 */
+    #hashFunc(key) {
+        return key % this.#capacity;
+    }
+
+    /* 负载因子 */
+    #loadFactor() {
+        return this.#size / this.#capacity;
+    }
+
+    /* 查询操作 */
+    get(key) {
+        const index = this.#hashFunc(key);
+        const bucket = this.#buckets[index];
+        // 遍历桶，若找到 key 则返回对应 val
+        for (const pair of bucket) {
+            if (pair.key === key) {
+                return pair.val;
+            }
+        }
+        // 若未找到 key 则返回 null
+        return null;
+    }
+
+    /* 添加操作 */
+    put(key, val) {
+        // 当负载因子超过阈值时，执行扩容
+        if (this.#loadFactor() > this.#loadThres) {
+            this.#extend();
+        }
+        const index = this.#hashFunc(key);
+        const bucket = this.#buckets[index];
+        // 遍历桶，若遇到指定 key ，则更新对应 val 并返回
+        for (const pair of bucket) {
+            if (pair.key === key) {
+                pair.val = val;
+                return;
+            }
+        }
+        // 若无该 key ，则将键值对添加至尾部
+        const pair = new Pair(key, val);
+        bucket.push(pair);
+        this.#size++;
+    }
+
+    /* 删除操作 */
+    remove(key) {
+        const index = this.#hashFunc(key);
+        let bucket = this.#buckets[index];
+        // 遍历桶，从中删除键值对
+        for (let i = 0; i < bucket.length; i++) {
+            if (bucket[i].key === key) {
+                bucket.splice(i, 1);
+                this.size--;
+                break;
+            }
+        }
+    }
+
+    /* 扩容哈希表 */
+    #extend() {
+        // 暂存原哈希表
+        const bucketsTmp = this.#buckets;
+        // 初始化扩容后的新哈希表
+        this.#capacity *= this.#extendRatio;
+        this.#buckets = new Array(this.#capacity).fill(null).map((x) => []);
+        this.#size = 0;
+        // 将键值对从原哈希表搬运至新哈希表
+        for (const bucket of bucketsTmp) {
+            for (const pair of bucket) {
+                this.put(pair.key, pair.val);
+            }
+        }
+    }
+
+    /* 打印哈希表 */
+    print() {
+        for (const bucket of this.#buckets) {
+            let res = [];
+            for (const pair of bucket) {
+                res.push(pair.key + ' -> ' + pair.val);
+            }
+            console.log(res);
+        }
+    }
+}
+
+/* Driver Code */
+/* 初始化哈希表 */
+const map = new 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');
+console.log('\n添加完成后，哈希表为\nKey -> Value');
+map.print();
+
+/* 查询操作 */
+// 向哈希表输入键 key ，得到值 value
+const name = map.get(13276);
+console.log('\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);
+console.log('\n删除 12836 后，哈希表为\nKey -> Value');
+map.print();

codes/javascript/chapter_hashing/hash_map_open_addressing.js

@@ -0,0 +1,162 @@
+/**
+ * File: hash_map_open_addressing.js
+ * Created Time: 2023-08-06
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* 键值对 Number -> String */
+class Pair {
+    constructor(key, val) {
+        this.key = key;
+        this.val = val;
+    }
+}
+
+/* 开放寻址哈希表 */
+class HashMapOpenAddressing {
+    #size; // 键值对数量
+    #capacity; // 哈希表容量
+    #loadThres; // 触发扩容的负载因子阈值
+    #extendRatio; // 扩容倍数
+    #buckets; // 桶数组
+    #removed; // 删除标记
+
+    /* 构造方法 */
+    constructor() {
+        this.#size = 0;
+        this.#capacity = 4;
+        this.#loadThres = 2.0 / 3.0;
+        this.#extendRatio = 2;
+        this.#buckets = new Array(this.#capacity).fill(null);
+        this.#removed = new Pair(-1, '-1');
+    }
+
+    /* 哈希函数 */
+    #hashFunc(key) {
+        return key % this.#capacity;
+    }
+
+    /* 负载因子 */
+    #loadFactor() {
+        return this.#size / this.#capacity;
+    }
+
+    /* 查询操作 */
+    get(key) {
+        const index = this.#hashFunc(key);
+        // 线性探测，从 index 开始向后遍历
+        for (let i = 0; i < this.#capacity; i++) {
+            // 计算桶索引，越过尾部返回头部
+            const j = (index + i) % this.#capacity;
+            // 若遇到空桶，说明无此 key ，则返回 null
+            if (this.#buckets[j] === null) return null;
+            // 若遇到指定 key ，则返回对应 val
+            if (
+                this.#buckets[j].key === key &&
+                this.#buckets[j][key] !== this.#removed.key
+            )
+                return this.#buckets[j].val;
+        }
+        return null;
+    }
+
+    /* 添加操作 */
+    put(key, val) {
+        // 当负载因子超过阈值时，执行扩容
+        if (this.#loadFactor() > this.#loadThres) {
+            this.#extend();
+        }
+        const index = this.#hashFunc(key);
+        // 线性探测，从 index 开始向后遍历
+        for (let i = 0; i < this.#capacity; i++) {
+            // 计算桶索引，越过尾部返回头部
+            let j = (index + i) % this.#capacity;
+            // 若遇到空桶、或带有删除标记的桶，则将键值对放入该桶
+            if (
+                this.#buckets[j] === null ||
+                this.#buckets[j][key] === this.#removed.key
+            ) {
+                this.#buckets[j] = new Pair(key, val);
+                this.#size += 1;
+                return;
+            }
+            // 若遇到指定 key ，则更新对应 val
+            if (this.#buckets[j].key === key) {
+                this.#buckets[j].val = val;
+                return;
+            }
+        }
+    }
+
+    /* 删除操作 */
+    remove(key) {
+        const index = this.#hashFunc(key);
+        // 线性探测，从 index 开始向后遍历
+        for (let i = 0; i < this.#capacity; i++) {
+            // 计算桶索引，越过尾部返回头部
+            const j = (index + i) % this.#capacity;
+            // 若遇到空桶，说明无此 key ，则直接返回
+            if (this.#buckets[j] === null) {
+                return;
+            }
+            // 若遇到指定 key ，则标记删除并返回
+            if (this.#buckets[j].key === key) {
+                this.#buckets[j] = this.#removed;
+                this.#size -= 1;
+                return;
+            }
+        }
+    }
+
+    /* 扩容哈希表 */
+    #extend() {
+        // 暂存原哈希表
+        const bucketsTmp = this.#buckets;
+        // 初始化扩容后的新哈希表
+        this.#capacity *= this.#extendRatio;
+        this.#buckets = new Array(this.#capacity).fill(null);
+        this.#size = 0;
+        // 将键值对从原哈希表搬运至新哈希表
+        for (const pair of bucketsTmp) {
+            if (pair !== null && pair.key !== this.#removed.key) {
+                this.put(pair.key, pair.val);
+            }
+        }
+    }
+
+    /* 打印哈希表 */
+    print() {
+        for (const pair of this.#buckets) {
+            if (pair !== null) {
+                console.log(pair.key + ' -> ' + pair.val);
+            } else {
+                console.log('null');
+            }
+        }
+    }
+}
+
+/* Driver Code */
+/* 初始化哈希表 */
+let map = new HashMapOpenAddressing();
+
+/* 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');
+console.log('\n添加完成后，哈希表为\nKey -> Value');
+map.print();
+
+/* 查询操作 */
+// 向哈希表输入键 key ，得到值 value
+const name = map.get(13276);
+console.log('\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(16750);
+console.log('\n删除 16750 后，哈希表为\nKey -> Value');
+map.print();

codes/javascript/chapter_hashing/simple_hash.js

@@ -0,0 +1,60 @@
+/**
+ * File: simple_hash.js
+ * Created Time: 2023-08-06
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* 加法哈希 */
+function addHash(key) {
+    let hash = 0;
+    const MODULUS = 1000000007;
+    for (const c of key) {
+        hash = (hash + c.charCodeAt(0)) % MODULUS;
+    }
+    return hash;
+}
+
+/* 乘法哈希 */
+function mulHash(key) {
+    let hash = 0;
+    const MODULUS = 1000000007;
+    for (const c of key) {
+        hash = (31 * hash + c.charCodeAt(0)) % MODULUS;
+    }
+    return hash;
+}
+
+/* 异或哈希 */
+function xorHash(key) {
+    let hash = 0;
+    const MODULUS = 1000000007;
+    for (const c of key) {
+        hash ^= c.charCodeAt(0);
+    }
+    return hash & MODULUS;
+}
+
+/* 旋转哈希 */
+function rotHash(key) {
+    let hash = 0;
+    const MODULUS = 1000000007;
+    for (const c of key) {
+        hash = ((hash << 4) ^ (hash >> 28) ^ c.charCodeAt(0)) % MODULUS;
+    }
+    return hash;
+}
+
+/* Driver Code */
+const key = 'Hello 算法';
+
+let hash = addHash(key);
+console.log('加法哈希值为 ' + hash);
+
+hash = mulHash(key);
+console.log('乘法哈希值为 ' + hash);
+
+hash = xorHash(key);
+console.log('异或哈希值为 ' + hash);
+
+hash = rotHash(key);
+console.log('旋转哈希值为 ' + hash);