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amejiarosarioamejiarosario
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5 files changed

+120
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lines changed

‎lib/data-structures/linked-lists/linked-list-1.js‎

Lines changed: 80 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,80 @@
1+
const Node = require('./node');
2+
3+
/**
4+
* Singly linked list
5+
*/
6+
class LinkedList {
7+
constructor() {
8+
this.root = null;
9+
}
10+
11+
/**
12+
* Adds element to the end of the list (tail)
13+
* Runtime: O(n)
14+
* @param {any} value
15+
*/
16+
addLast(value) { // similar Array.push
17+
const node = new Node(value);
18+
19+
if(this.root) {
20+
let currentNode = this.root;
21+
while(currentNode && currentNode.next) {
22+
currentNode = currentNode.next;
23+
}
24+
currentNode.next = node;
25+
} else {
26+
this.root = node;
27+
}
28+
}
29+
30+
/**
31+
* Removes element from the start of the list (head/root)
32+
* Runtime: O(1)
33+
*/
34+
removeFirst() { // similar Array.shift
35+
const first = this.root;
36+
37+
if(first) {
38+
this.root = first.next;
39+
return first.value;
40+
}
41+
}
42+
43+
/**
44+
* Adds element to the begining of the list
45+
* Runtime: O(1)
46+
* @param {any} value
47+
*/
48+
addFirst(value) { // similar to Array.unshift
49+
const node = new Node(value);
50+
node.next = this.root;
51+
this.root = node;
52+
}
53+
54+
/**
55+
* Removes element to the end of the list
56+
* similar to Array.pop
57+
* Runtime: O(n)
58+
*/
59+
removeLast() {
60+
let current = this.root;
61+
let target;
62+
63+
if(current && current.next) {
64+
while(current && current.next && current.next.next) {
65+
current = current.next;
66+
}
67+
target = current.next;
68+
current.next = null;
69+
} else {
70+
this.root = null;
71+
target = current;
72+
}
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74+
if(target) {
75+
return target.value;
76+
}
77+
}
78+
}
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80+
module.exports = LinkedList;

‎lib/data-structures/linked-lists/linked-list.js‎

Lines changed: 16 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -5,50 +5,50 @@ const Node = require('./node');
55
*/
66
class LinkedList {
77
constructor() {
8-
this.root = null;
8+
this.first = null; // head/root element
99
}
1010

1111
/**
12-
* Adds element to the end of the list (tail)
12+
* Adds element to the end of the list (tail). Similar to Array.push
1313
* Runtime: O(n)
1414
* @param {any} value
1515
*/
16-
addLast(value) { // similar Array.push
16+
addLast(value) {
1717
const node = new Node(value);
1818

19-
if(this.root) {
20-
let currentNode = this.root;
19+
if(this.first) {
20+
let currentNode = this.first;
2121
while(currentNode && currentNode.next) {
2222
currentNode = currentNode.next;
2323
}
2424
currentNode.next = node;
2525
} else {
26-
this.root = node;
26+
this.first = node;
2727
}
2828
}
2929

3030
/**
31-
* Removes element from the start of the list (head/root)
31+
* Removes element from the start of the list (head/root). similar Array.shift
3232
* Runtime: O(1)
3333
*/
34-
removeFirst() { // similar Array.shift
35-
const first = this.root;
34+
removeFirst() {
35+
const first = this.first;
3636

3737
if(first) {
38-
this.root = first.next;
38+
this.first = first.next;
3939
return first.value;
4040
}
4141
}
4242

4343
/**
44-
* Adds element to the begining of the list
44+
* Adds element to the begining of the list. Similar to Array.unshift
4545
* Runtime: O(1)
4646
* @param {any} value
4747
*/
48-
addFirst(value) { // similar to Array.unshift
48+
addFirst(value) {
4949
const node = new Node(value);
50-
node.next = this.root;
51-
this.root = node;
50+
node.next = this.first;
51+
this.first = node;
5252
}
5353

5454
/**
@@ -57,7 +57,7 @@ class LinkedList {
5757
* Runtime: O(n)
5858
*/
5959
removeLast() {
60-
let current = this.root;
60+
let current = this.first;
6161
let target;
6262

6363
if(current && current.next) {
@@ -67,7 +67,7 @@ class LinkedList {
6767
target = current.next;
6868
current.next = null;
6969
} else {
70-
this.root = null;
70+
this.first = null;
7171
target = current;
7272
}
7373

‎lib/data-structures/linked-lists/linked-list.spec.js‎

Lines changed: 11 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -10,17 +10,17 @@ describe('LinkedList', function () {
1010
describe('#addLast', () => {
1111
it('should add element to end/tail of the list', () => {
1212
linkedList.addLast('a');
13-
expect(linkedList.root.value).toBe('a');
13+
expect(linkedList.first.value).toBe('a');
1414
});
1515

1616
it('should link values', () => {
1717
linkedList.addLast('a');
1818
linkedList.addLast('b');
1919
linkedList.addLast('c');
2020

21-
expect(linkedList.root.value).toBe('a');
22-
expect(linkedList.root.next.value).toBe('b');
23-
expect(linkedList.root.next.next.value).toBe('c');
21+
expect(linkedList.first.value).toBe('a');
22+
expect(linkedList.first.next.value).toBe('b');
23+
expect(linkedList.first.next.next.value).toBe('c');
2424
});
2525
});
2626

@@ -32,8 +32,8 @@ describe('LinkedList', function () {
3232

3333
it('should remove first item: a', () => {
3434
expect(linkedList.removeFirst()).toBe('a');
35-
expect(linkedList.root.value).toBe('b');
36-
expect(linkedList.root.next).toBe(null);
35+
expect(linkedList.first.value).toBe('b');
36+
expect(linkedList.first.next).toBe(null);
3737

3838
expect(linkedList.removeFirst()).toBe('b');
3939
expect(linkedList.removeFirst()).toBe(undefined);
@@ -44,14 +44,14 @@ describe('LinkedList', function () {
4444
describe('#addFirst', () => {
4545
it('add element to the head/root of the list', () => {
4646
linkedList.addFirst('a');
47-
expect(linkedList.root.value).toBe('a');
47+
expect(linkedList.first.value).toBe('a');
4848
});
4949

5050
it('add element to the head/root of the list', () => {
5151
linkedList.addFirst('a');
5252
linkedList.addFirst('b');
53-
expect(linkedList.root.value).toBe('b');
54-
expect(linkedList.root.next.value).toBe('a');
53+
expect(linkedList.first.value).toBe('b');
54+
expect(linkedList.first.next.value).toBe('a');
5555
});
5656
});
5757

@@ -65,8 +65,8 @@ describe('LinkedList', function () {
6565
it('should remove first item', () => {
6666
expect(linkedList.removeLast()).toBe('c');
6767
expect(linkedList.removeLast()).toBe('b');
68-
expect(linkedList.root.value).toBe('a');
69-
expect(linkedList.root.next).toBe(null);
68+
expect(linkedList.first.value).toBe('a');
69+
expect(linkedList.first.next).toBe(null);
7070

7171
expect(linkedList.removeLast()).toBe('a');
7272
expect(linkedList.removeLast()).toBe(undefined);

‎lib/data-structures/linked-lists/node-1.js‎

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,11 @@
1+
/**
2+
* Simple node
3+
*/
4+
class Node {
5+
constructor(value) {
6+
this.value = value;
7+
this.next = null;
8+
}
9+
}
10+
11+
module.exports = Node;

‎lib/data-structures/linked-lists/node.js‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,10 +1,11 @@
11
/**
2-
* Simple node
2+
* Node with reference to next and previous element
33
*/
44
class Node {
55
constructor(value) {
66
this.value = value;
77
this.next = null;
8+
this.previous = null;
89
}
910
}
1011

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