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e97eee0e18
* refactor(chapter_hashing): Remove unnecessary chaining operator * feat(chapter_hashing): Add js and ts codes for chapter 6 * refactor(chapter_hashing): Optimize the remove function logic * refactor(chapter_hashing): Remove unnecessary chaining operator * refactor(chapter_hashing): use const instead of let
142 lines
3.7 KiB
JavaScript
142 lines
3.7 KiB
JavaScript
/**
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* File: hash_map_chaining.js
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* Created Time: 2023-08-06
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* Author: yuan0221 (yl1452491917@gmail.com)
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*/
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/* 键值对 Number -> String */
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class Pair {
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constructor(key, val) {
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this.key = key;
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this.val = val;
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}
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}
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/* 链式地址哈希表 */
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class HashMapChaining {
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#size; // 键值对数量
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#capacity; // 哈希表容量
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#loadThres; // 触发扩容的负载因子阈值
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#extendRatio; // 扩容倍数
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#buckets; // 桶数组
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/* 构造方法 */
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constructor() {
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this.#size = 0;
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this.#capacity = 4;
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this.#loadThres = 2 / 3.0;
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this.#extendRatio = 2;
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this.#buckets = new Array(this.#capacity).fill(null).map((x) => []);
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}
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/* 哈希函数 */
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#hashFunc(key) {
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return key % this.#capacity;
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}
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/* 负载因子 */
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#loadFactor() {
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return this.#size / this.#capacity;
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}
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/* 查询操作 */
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get(key) {
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const index = this.#hashFunc(key);
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const bucket = this.#buckets[index];
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// 遍历桶,若找到 key 则返回对应 val
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for (const pair of bucket) {
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if (pair.key === key) {
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return pair.val;
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}
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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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put(key, val) {
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// 当负载因子超过阈值时,执行扩容
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if (this.#loadFactor() > this.#loadThres) {
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this.#extend();
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}
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const index = this.#hashFunc(key);
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const bucket = this.#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 (const pair of bucket) {
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if (pair.key === key) {
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pair.val = val;
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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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const pair = new Pair(key, val);
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bucket.push(pair);
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this.#size++;
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}
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/* 删除操作 */
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remove(key) {
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const index = this.#hashFunc(key);
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let bucket = this.#buckets[index];
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// 遍历桶,从中删除键值对
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for (let i = 0; i < bucket.length; i++) {
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if (bucket[i].key === key) {
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bucket.splice(i, 1);
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this.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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#extend() {
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// 暂存原哈希表
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const bucketsTmp = this.#buckets;
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// 初始化扩容后的新哈希表
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this.#capacity *= this.#extendRatio;
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this.#buckets = new Array(this.#capacity).fill(null).map((x) => []);
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this.#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 (const bucket of bucketsTmp) {
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for (const pair of bucket) {
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this.put(pair.key, 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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print() {
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for (const bucket of this.#buckets) {
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let res = [];
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for (const pair of bucket) {
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res.push(pair.key + ' -> ' + pair.val);
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}
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console.log(res);
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}
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}
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}
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/* Driver Code */
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/* 初始化哈希表 */
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const map = new 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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console.log('\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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const name = map.get(13276);
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console.log('\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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console.log('\n删除 12836 后,哈希表为\nKey -> Value');
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map.print();
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