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/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
"use strict";
/**
* @template T
*/
class Queue {
/**
* @param {Iterable<T>=} items The initial elements.
*/
constructor(items) {
/** @private @type {Set<T>} */
this._set = new Set(items);
/** @private @type {Iterator<T>} */
this._iterator = this._set[Symbol.iterator]();
}
/**
* Returns the number of elements in this queue.
* @returns {number} The number of elements in this queue.
*/
get length() {
return this._set.size;
}
/**
* Appends the specified element to this queue.
* @param {T} item The element to add.
* @returns {void}
*/
enqueue(item) {
this._set.add(item);
}
/**
* Retrieves and removes the head of this queue.
* @returns {T | undefined} The head of the queue of `undefined` if this queue is empty.
*/
dequeue() {
const result = this._iterator.next();
if (result.done) return undefined;
this._set.delete(result.value);
return result.value;
}
}
module.exports = Queue;
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