JavaScript資料結構與演算法-散列練習

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散列的實現

// 散列類 - 線性探測法function HashTable () {    this.table = new Array(137);    this.values = [];    this.simpleHash = simpleHash;    this.betterHash = betterHash;    this.showDistro = showDistro;    this.put = put;    this.get = get;}function put (key, data) {    let pos = this.betterHash(key);    // this.table[pos] = data;    if (this.table[pos] === undefined) {        this.table[pos] = key;        this.values[pos] = data;    } else {        while (this.table[pos] !== undefined) {            ++pos;        }        this.table[pos] = key;        this.values[pos] = data;    }}function get (key) {    // return this.table[this.betterHash(key)];    let hash = -1;    hash = this.betterHash(key);    if (hash > -1) {        for (let i = hash; this.table[hash] !== undefined; ++i) {            if (this.table[hash] === key) {                return this.values[hash];            }        }    }    return undefined;}function simpleHash (data) {    let total = 0;    for (let i = 0; i < data.length; ++i) {        total += data.charCodeAt(i);    }    return total % this.table.length;}function showDistro () {    let n = 0;    for (let i = 0; i < this.table.length; ++i) {        if (this.table[i] !== undefined) {            console.log(`${i}: ${this.table[i]}`);        }    }}function betterHash (string) {    const H = 7;    let total = 0;    for (let i = 0; i < string.length; ++i) {        total += H * total + string.charCodeAt(i);    }    total = total % this.table.length;    if (total < 0) {        total += this.table.length -1;    }    return parseInt(total, 10);}

練習使用線性探測法建立一個字典，用來儲存單詞的定義。該程式需要包含兩個部分：第一部分將一組單詞和它們的定義儲存進散列表；第二部分讓使用者輸入單詞，程式給出該單詞的定義。

// 字典類function Dict () {    this.hashTable = new HashTable();    this.save = save;    this.find = find;}function save (word, description) {    this.hashTable.put(word, description);}function find (word) {    return this.hashTable.get(word);}// 樣本let d = new Dict();d.save('Mazey', 'a strong man.');d.save('Cherrie', 'a beautiful girl.');d.save('John', 'unknown.');console.log(d.find('John')); // unknown.console.log(d.find('Mazey')); // a strong man.console.log(d.find('Ada')); // undefined

JavaScript資料結構與演算法-散列練習