43 lines
639 B
JavaScript
43 lines
639 B
JavaScript
"use strict";
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module.exports = class Queue {
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constructor(items) {
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this.first = null;
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this.last = null;
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this.length = 0;
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if(items) {
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for(const item of items) {
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this.enqueue(item);
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}
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}
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}
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enqueue(item) {
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const first = this.first;
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const node = {
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item,
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next: null
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};
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if(first === null) {
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this.last = node;
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} else {
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first.next = node;
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}
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this.first = node;
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this.length++;
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}
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dequeue() {
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const last = this.last;
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if(last === null)
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return undefined;
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const next = last.next;
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if(next === null) {
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this.first = null;
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}
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this.last = next;
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this.length--;
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return last.item;
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}
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};
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