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Commit 5bec3a5

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Merge pull request #80 from knaxus/queue
Re-implementation of Queue
2 parents 01b9a6f + d48713c commit 5bec3a5

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6 files changed

+109
-46
lines changed

6 files changed

+109
-46
lines changed

‎src/_DataStructures_/LinkedList/index.js‎

Lines changed: 8 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -22,13 +22,16 @@ class LinkedList {
2222
}
2323

2424
addAtEnd(element) {
25+
const node = new Node(element, null);
26+
this.size += 1;
27+
2528
if (!this.head) {
26-
return this.addAtBeginning(element);
29+
this.head = node;
30+
this.tail = node;
31+
return node;
2732
}
28-
const node = new Node(element, null);
2933
this.tail.next = node;
3034
this.tail = node;
31-
this.size += 1;
3235
return node;
3336
}
3437

@@ -42,6 +45,7 @@ class LinkedList {
4245
const node = this.head;
4346
this.head = this.head.next;
4447
this.size -= 1;
48+
node.next = null;
4549
return node;
4650
}
4751

@@ -139,6 +143,7 @@ class LinkedList {
139143
const node = address;
140144
previous.next = address.next.next;
141145
this.size -= 1;
146+
node.next = null;
142147
return node;
143148
}
144149

‎src/_DataStructures_/Queue/Queue.test.js‎

Lines changed: 21 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -12,23 +12,24 @@ describe('Data Structure : Queue', () => {
1212
queue = new Queue();
1313
});
1414

15-
it('Should add() element to a queue', () => {
16-
queue.add(5);
17-
expect(queue.data).toEqual([5]);
15+
it('Should add element to a queue', () => {
16+
queue.enqueue(5);
17+
expect(queue.peek()).toEqual(5);
1818
});
1919

20-
it('Should remove() an element from the queue', () => {
21-
queue.add(2);
22-
queue.add(3);
20+
it('Should dequeue() an element from the queue', () => {
21+
queue.enqueue(2);
22+
queue.enqueue(3);
2323

24-
expect(queue.remove()).toEqual(2);
25-
expect(queue.data).toEqual([3]);
24+
expect(queue.dequeue()).toEqual(2);
25+
expect(queue.peek()).toEqual(3);
26+
expect(queue.length()).toEqual(1);
2627
});
2728

2829
describe('peek()', () => {
2930
beforeEach(() => {
30-
queue.add(2);
31-
queue.add(5);
31+
queue.enqueue(2);
32+
queue.enqueue(5);
3233
});
3334

3435
it('Should return the elemet to be removed using peek()', () => {
@@ -37,21 +38,21 @@ describe('Data Structure : Queue', () => {
3738

3839
it('Should not remove the element', () => {
3940
expect(queue.peek()).toEqual(2);
40-
expect(queue.remove()).toEqual(2);
41+
expect(queue.dequeue()).toEqual(2);
4142
});
4243
});
4344

4445
it('Should maintain the order of elements', () => {
4546
// first in first out
46-
queue.add(2);
47-
queue.add(1);
48-
queue.add(4);
49-
queue.add(3);
50-
51-
expect(queue.remove()).toEqual(2);
52-
expect(queue.remove()).toEqual(1);
53-
expect(queue.remove()).toEqual(4);
54-
expect(queue.remove()).toEqual(3);
47+
queue.enqueue(2);
48+
queue.enqueue(1);
49+
queue.enqueue(4);
50+
queue.enqueue(3);
51+
52+
expect(queue.dequeue()).toEqual(2);
53+
expect(queue.dequeue()).toEqual(1);
54+
expect(queue.dequeue()).toEqual(4);
55+
expect(queue.dequeue()).toEqual(3);
5556
});
5657
});
5758
});
Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,20 @@
1+
class Queue {
2+
constructor() {
3+
this.data = [];
4+
}
5+
6+
add(element) {
7+
// add element to the start of the data
8+
return this.data.unshift(element);
9+
}
10+
11+
peek() {
12+
return this.data[this.data.length - 1];
13+
}
14+
15+
remove() {
16+
return this.data.pop();
17+
}
18+
}
19+
20+
module.exports = Queue;

‎src/_DataStructures_/Queue/index.js‎

Lines changed: 46 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -1,20 +1,57 @@
1-
class Queue {
1+
const { LinkedList: SinglyLinkedLists } = require('../LinkedList');
2+
3+
class Queue extends SinglyLinkedLists {
24
constructor() {
3-
this.data = [];
5+
super();
6+
this.NotAllowed = 'Not Allowed';
7+
}
8+
9+
enqueue(data) {
10+
return this.addAtEnd(data);
411
}
512

6-
add(element) {
7-
// add element to the start of the data
8-
return this.data.unshift(element);
13+
dequeue() {
14+
constnode=this.removeFromBeginning();
15+
return node ? node.data : node;
916
}
1017

1118
peek() {
12-
return this.data[this.data.length - 1];
19+
const node = this.getFirst();
20+
return node ? node.data : node;
21+
}
22+
23+
length() {
24+
return this.size;
25+
}
26+
27+
destroy() {
28+
this.delete();
29+
}
30+
31+
/** Override and throw error for other LL methods */
32+
addAtBeginning() {
33+
throw new Error(this.NotAllowed);
34+
}
35+
36+
addAt() {
37+
throw new Error(this.NotAllowed);
38+
}
39+
40+
removeFromEnd() {
41+
throw new Error(this.NotAllowed);
42+
}
43+
44+
getLast() {
45+
throw new Error(this.NotAllowed);
46+
}
47+
48+
getAt() {
49+
throw new Error(this.NotAllowed);
1350
}
1451

15-
remove() {
16-
returnthis.data.pop();
52+
removeAt() {
53+
thrownewError(this.NotAllowed);
1754
}
1855
}
1956

20-
module.exports = Queue;
57+
module.exports = Queue;

‎src/_DataStructures_/Queue/weave/index.js‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -4,12 +4,12 @@ function weaveQueues(first, second) {
44
const weaved = new Queue();
55

66
while (first.peek() || second.peek()) {
7-
if (first.peek()!==undefined) {
8-
weaved.add(first.remove());
7+
if (first.peek()) {
8+
weaved.enqueue(first.dequeue());
99
}
1010

11-
if (second.peek()!==undefined) {
12-
weaved.add(second.remove());
11+
if (second.peek()) {
12+
weaved.enqueue(second.dequeue());
1313
}
1414
}
1515
return weaved;

‎src/_DataStructures_/Queue/weave/weave.test.js‎

Lines changed: 10 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -10,18 +10,18 @@ describe('Weave two queues using weaveQueues()', () => {
1010
const q1 = new Queue();
1111
const q2 = new Queue();
1212

13-
q1.add('Hello');
14-
q2.add(1);
15-
q1.add('World');
16-
q2.add(2);
17-
q2.add(3);
13+
q1.enqueue('Hello');
14+
q2.enqueue(1);
15+
q1.enqueue('World');
16+
q2.enqueue(2);
17+
q2.enqueue(3);
1818

1919
const q3 = weaveQueues(q1, q2);
2020

21-
expect(q3.remove()).toEqual('Hello');
22-
expect(q3.remove()).toEqual(1);
23-
expect(q3.remove()).toEqual('World');
24-
expect(q3.remove()).toEqual(2);
25-
expect(q3.remove()).toEqual(3);
21+
expect(q3.dequeue()).toEqual('Hello');
22+
expect(q3.dequeue()).toEqual(1);
23+
expect(q3.dequeue()).toEqual('World');
24+
expect(q3.dequeue()).toEqual(2);
25+
expect(q3.dequeue()).toEqual(3);
2626
});
2727
});

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