-
Notifications
You must be signed in to change notification settings - Fork 31k
Expand file tree
/
Copy pathQueue.js
More file actions
58 lines (51 loc) · 1.41 KB
/
Copy pathQueue.js
File metadata and controls
58 lines (51 loc) · 1.41 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
import LinkedList from '../linked-list/LinkedList';
export default class Queue {
constructor() {
// We're going to implement Queue based on LinkedList since the two
// structures are quite similar. Namely, they both operate mostly on
// the elements at the beginning and the end. Compare enqueue/dequeue
// operations of Queue with append/deleteHead operations of LinkedList.
this.linkedList = new LinkedList();
}
/**
* @return {boolean}
*/
isEmpty() {
return !this.linkedList.head;
}
/**
* Read the element at the front of the queue without removing it.
* @return {*}
*/
peek() {
if (this.isEmpty()) {
return null;
}
return this.linkedList.head.value;
}
/**
* Add a new element to the end of the queue (the tail of the linked list).
* This element will be processed after all elements ahead of it.
* @param {*} value
*/
enqueue(value) {
this.linkedList.append(value);
}
/**
* Remove the element at the front of the queue (the head of the linked list).
* If the queue is empty, return null.
* @return {*}
*/
dequeue() {
const removedHead = this.linkedList.deleteHead();
return removedHead ? removedHead.value : null;
}
/**
* @param [callback]
* @return {string}
*/
toString(callback) {
// Return string representation of the queue's linked list.
return this.linkedList.toString(callback);
}
}