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<h1 class="page-title">Source: data-structures/hash-table.js</h1>

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<pre class="prettyprint source linenums"><code>/**

* Hash Table

*

* An associative array, that can map keys

* (strings and numbers) to values in O(1).

*

* @example

* var hash = require('path-to-algorithms/src/data-structures'+

* '/hash-table');

* var hashTable = new hash.Hashtable();

*

* hashTable.put(10, 'value');

* hashTable.put('key', 10);

*

* console.log(hashTable.get(10)); // 'value'

* console.log(hashTable.get('key')); // 10

*

* hashTable.remove(10);

* hashTable.remove('key');

*

* console.log(hashTable.get(10)); // undefined

* console.log(hashTable.get('key')); // undefined

*

* @module data-structures/hash-table

*/

(function (exports) {

'use strict';

/**

* Constructs a Node to store data and next/prev nodes in Hash table.

*

* @public

* @constructor

* @param {Number|String} key Key of the node.

* @param {Number|String} data Data to be stored in hash table.

*/

exports.Node = function (key, data) {

this.key = key;

this.data = data;

this.next = undefined;

this.prev = undefined;

};

/**

* Construct a Hash table..

*

* @public

* @constructor

*/

exports.Hashtable = function () {

this.buckets = [];

// The higher the bucket count; less likely for collisions.

this.maxBucketCount = 100;

};

/**

* Simple non-crypto hash used to hash keys, which determines

* while bucket the value will be placed in.

* A javascript implementation of Java's 32bitint hash.

*

* @public

* @method

* @param {Number|String} val Key to be hashed.

*/

exports.Hashtable.prototype.hashCode = function (val) {

var i;

var hashCode = 0;

var character;

// If value to be hashed is already an integer, return it.

if (val.length === 0 || val.length === undefined) {

return val;

}

for (i = 0; i &lt; val.length; i += 1) {

character = val.charCodeAt(i);

/*jshint -W016 */

hashCode = ((hashCode &lt;&lt; 5) - hashCode) + character;

hashCode = hashCode &amp; hashCode;

/*jshint -W016 */

}

return hashCode;

};

/**

* Puts data into the table based on hashed key value.

*

* @public

* @method

* @param {Number|String} key Key for data.

* @param {Number|String} data Data to be stored in table.

*/

exports.Hashtable.prototype.put = function (key, data, hashCode) {

/*

Make collision testing easy with optional hashCode parameter.

That should not be used! Only by spec/tests.

*/

if (hashCode === undefined) {

// Typical use

hashCode = this.hashCode(key);

} else if (hashCode.length > 0) {

// Testing/Spec - String hash passed, convert to int based hash.

hashCode = this.hashCode(hashCode);

}

// Adjust hash to fit within buckets.

hashCode = hashCode % this.maxBucketCount;

var newNode = new exports.Node(key, data);

// No element exists at hash/index for given key -> put in table.

if (this.buckets[hashCode] === undefined) {

this.buckets[hashCode] = newNode;

return;

}

// Element exists at hash/index for given key, but, same key -> overwrite.

if (this.buckets[hashCode].key === key) {

this.buckets[hashCode].data = data;

return;

}

/*

Item exists at hash/index for key, but different key.

Handle collision.

*/

var first = this.buckets[hashCode];

while (first.next !== undefined) {

first = first.next;

}

first.next = newNode;

newNode.prev = first;

};

/**

* Get's data from the table based on key.

*

* @public

* @method

* @param {Number|String} key Key for data to be retrieved.

*/

exports.Hashtable.prototype.get = function (key, hashCode) {

/*

Make collision testing easy with optional hashCode parameter.

That should not be used! Only by spec/tests.

*/

if (hashCode === undefined) {

// Typical use

hashCode = this.hashCode(key);

} else if (hashCode.length > 0) {

// Testing/Spec - String hash passed, convert to int based hash.

hashCode = this.hashCode(hashCode);

}

hashCode = hashCode % this.maxBucketCount;

if (this.buckets[hashCode] === undefined) {

return undefined;

} else if (

this.buckets[hashCode].next === undefined &amp;&amp;

this.buckets[hashCode].key === key

) {

return this.buckets[hashCode].data;

} else {

var first = this.buckets[hashCode];

while (

first !== undefined &amp;&amp;

first.next !== undefined &amp;&amp;

first.key !== key

) {

first = first.next;

}

if (first.key === key) {

return first.data;

} else {

return undefined;

}

}

};

/**

* Removes data from the table based on key.

*

* @public

* @method

* @param {Number|String} key Key of the data to be removed.

*/

exports.Hashtable.prototype.remove = function (key, hashCode) {

/*

Make collision testing easy with optional hashCode parameter.

That should not be used! Only by spec/tests.

*/

if (hashCode === undefined) {

// Typical use

hashCode = this.hashCode(key);

} else if (hashCode.length > 0) {

// Testing/Spec - String hash passed, convert to int based hash.

hashCode = this.hashCode(hashCode);

}

hashCode = hashCode % this.maxBucketCount;

if (this.buckets[hashCode] === undefined) {

return undefined;

} else if (this.buckets[hashCode].next === undefined) {

this.buckets[hashCode] = undefined;

} else {

var first = this.buckets[hashCode];

while (

first !== undefined &amp;&amp;

first.next !== undefined &amp;&amp;

first.key !== key

) {

first = first.next;

}

var removedValue = first.data;

// Removing (B)

// (B) : only item in bucket

if (first.prev === undefined &amp;&amp; first.next === undefined) {

first = undefined;

return removedValue;

}

// (B) - A - C: start link in bucket

if (first.prev === undefined &amp;&amp; first.next !== undefined) {

first.data = first.next.data;

first.key = first.next.key;

if (first.next.next !== undefined) {

first.next = first.next.next;

} else {

first.next = undefined;

}

return removedValue;

}

// A - (B) : end link in bucket

if (first.prev !== undefined &amp;&amp; first.next === undefined) {

first.prev.next = undefined;

first = undefined;

return removedValue;

}

// A - (B) - C : middle link in bucket

if (first.prev !== undefined &amp;&amp; first.next !== undefined) {

first.prev.next = first.next;

first.next.prev = first.prev;

first = undefined;

return removedValue;

}

}

};

})(typeof window === 'undefined' ? module.exports : window);

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