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clarify comments (#193)
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@ -2,10 +2,10 @@ import LinkedList from '../linked-list/LinkedList';
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export default class Queue {
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constructor() {
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// We're going to implement Queue based on LinkedList since this
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// structures a quite similar. Namely they both operates mostly with
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// with theirs beginning and the end. Compare enqueue/de-queue
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// operations of the Queue with append/prepend operations of LinkedList.
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// We're going to implement Queue based on LinkedList since the two
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// structures are quite similar. Namely, they both operate mostly on
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// the elements at the beginning and the end. Compare enqueue/dequeue
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// operations of Queue with append/deleteHead operations of LinkedList.
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this.linkedList = new LinkedList();
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}
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@ -13,39 +13,36 @@ export default class Queue {
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* @return {boolean}
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*/
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isEmpty() {
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// The queue is empty in case if its linked list don't have tail.
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return !this.linkedList.tail;
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return !this.linkedList.head;
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}
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/**
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* Read the element at the front of the queue without removing it.
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* @return {*}
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*/
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peek() {
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if (!this.linkedList.head) {
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// If linked list is empty then there is nothing to peek from.
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return null;
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}
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// Just read the value from the end of linked list without deleting it.
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return this.linkedList.head.value;
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}
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/**
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* Add a new element to the end of the queue (the tail of the linked list).
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* This element will be processed after all elements ahead of it.
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* @param {*} value
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*/
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enqueue(value) {
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// Enqueueing means to stand in the line. Therefore let's just add
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// new value at the beginning of the linked list. It will need to wait
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// until all previous nodes will be processed.
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this.linkedList.append(value);
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}
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/**
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* Remove the element at the front of the queue (the head of the linked list).
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* If the queue is empty, return null.
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* @return {*}
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*/
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dequeue() {
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// Let's try to delete the last node from linked list (the tail).
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// If there is no tail in linked list (it is empty) just return null.
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const removedHead = this.linkedList.deleteHead();
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return removedHead ? removedHead.value : null;
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}
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