Add Queue.

This commit is contained in:
Oleksii Trekhleb 2018-03-28 15:53:12 +03:00
parent 55d6aa5758
commit c8bfe9ffaa
8 changed files with 4059 additions and 25 deletions

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@ -6,6 +6,7 @@
- [Linked List](https://github.com/trekhleb/javascript-algorithms/tree/master/src/data-structures/linked-list)
- [Hash Table](https://github.com/trekhleb/javascript-algorithms/tree/master/src/data-structures/hash-table)
- [Queue](https://github.com/trekhleb/javascript-algorithms/tree/master/src/data-structures/queue)
## Running Tests

3855
package-lock.json generated

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@ -29,5 +29,8 @@
"eslint-plugin-jsx-a11y": "^6.0.3",
"eslint-plugin-react": "^7.7.0",
"jest": "^22.4.3"
},
"dependencies": {
"npm": "^5.8.0"
}
}

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@ -3,28 +3,7 @@ import LinkedListNode from './LinkedListNode';
export default class LinkedList {
constructor() {
this.head = null;
}
append({ value, key = null }) {
const newNode = new LinkedListNode({ value, key });
// If there is no head yet let's make new node a head.
if (!this.head) {
this.head = newNode;
return newNode;
}
// Rewind to last node.
let currentNode = this.head;
while (currentNode.next !== null) {
currentNode = currentNode.next;
}
// Attach new node to the end of linked list.
currentNode.next = newNode;
return newNode;
this.tail = null;
}
prepend({ value, key = null }) {
@ -36,12 +15,31 @@ export default class LinkedList {
return newNode;
}
append({ value, key = null }) {
const newNode = new LinkedListNode({ value, key });
// If there is no head yet let's make new node a head.
if (!this.head) {
this.head = newNode;
this.tail = newNode;
return newNode;
}
// Attach new node to the end of linked list.
this.tail.next = newNode;
this.tail = newNode;
return newNode;
}
appendUnique({ value, key = null }) {
const newNode = new LinkedListNode({ value, key });
// If there is no head yet let's make new node a head.
if (!this.head) {
this.head = newNode;
this.tail = newNode;
return newNode;
}
@ -66,6 +64,7 @@ export default class LinkedList {
// Attach new node to the end of linked list.
currentNode.next = newNode;
this.tail = newNode;
return newNode;
}
@ -90,9 +89,15 @@ export default class LinkedList {
if (currentNode.next.value === value) {
deletedNode = currentNode.next;
currentNode.next = currentNode.next.next;
}
} else {
currentNode = currentNode.next;
}
}
// Check if tail must be deleted.
if (this.tail.value === value) {
this.tail = currentNode;
}
return deletedNode;
}
@ -117,13 +122,44 @@ export default class LinkedList {
if (currentNode.next.key === key) {
deletedNode = currentNode.next;
currentNode.next = currentNode.next.next;
}
} else {
currentNode = currentNode.next;
}
}
// Check if tail must be deleted.
if (this.tail.key === key) {
this.tail = currentNode;
}
return deletedNode;
}
deleteTail() {
if (this.head === this.tail) {
const deletedTail = this.tail;
this.head = null;
this.tail = null;
return deletedTail;
}
const deletedTail = this.tail;
// Rewind to the last node and delete "next" link for the node before the last one.
let currentNode = this.head;
while (currentNode.next) {
if (!currentNode.next.next) {
currentNode.next = null;
} else {
currentNode = currentNode.next;
}
}
this.tail = currentNode;
return deletedTail;
}
findByKey(key) {
let currentNode = this.head;

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@ -9,6 +9,9 @@ describe('LinkedList', () => {
it('should append node to linked list', () => {
const linkedList = new LinkedList();
expect(linkedList.head).toBeNull();
expect(linkedList.tail).toBeNull();
const node1 = linkedList.append({ value: 1 });
const node2 = linkedList.append({ value: 2, key: 'test' });
@ -16,6 +19,9 @@ describe('LinkedList', () => {
expect(node2.value).toBe(2);
expect(node2.key).toBe('test');
expect(linkedList.head.toString()).toBe('1');
expect(linkedList.tail.toString()).toBe('test:2');
expect(linkedList.toString()).toBe('1,test:2');
});
@ -28,6 +34,9 @@ describe('LinkedList', () => {
expect(node1.value).toBe(1);
expect(node2.value).toBe(2);
expect(linkedList.head.toString()).toBe('2');
expect(linkedList.tail.toString()).toBe('1');
expect(linkedList.toString()).toBe('2,1');
});
@ -38,18 +47,61 @@ describe('LinkedList', () => {
linkedList.append({ value: 2 });
linkedList.append({ value: 3 });
linkedList.append({ value: 3 });
linkedList.append({ value: 3 });
linkedList.append({ value: 4 });
linkedList.append({ value: 5 });
expect(linkedList.head.toString()).toBe('1');
expect(linkedList.tail.toString()).toBe('5');
const deletedNode = linkedList.deleteByValue(3);
expect(deletedNode.value).toBe(3);
expect(linkedList.toString()).toBe('1,2,3,4,5');
expect(linkedList.toString()).toBe('1,2,4,5');
linkedList.deleteByValue(3);
expect(linkedList.toString()).toBe('1,2,4,5');
linkedList.deleteByValue(1);
expect(linkedList.toString()).toBe('2,4,5');
expect(linkedList.head.toString()).toBe('2');
expect(linkedList.tail.toString()).toBe('5');
linkedList.deleteByValue(5);
expect(linkedList.toString()).toBe('2,4');
expect(linkedList.head.toString()).toBe('2');
expect(linkedList.tail.toString()).toBe('4');
linkedList.deleteByValue(4);
expect(linkedList.toString()).toBe('2');
expect(linkedList.head.toString()).toBe('2');
expect(linkedList.tail.toString()).toBe('2');
});
it('should delete linked list tail', () => {
const linkedList = new LinkedList();
linkedList.append({ value: 1 });
linkedList.append({ value: 2 });
expect(linkedList.head.toString()).toBe('1');
expect(linkedList.tail.toString()).toBe('2');
const deletedNode1 = linkedList.deleteTail();
expect(deletedNode1.value).toBe(2);
expect(linkedList.toString()).toBe('1');
expect(linkedList.head.toString()).toBe('1');
expect(linkedList.tail.toString()).toBe('1');
const deletedNode2 = linkedList.deleteTail();
expect(deletedNode2.value).toBe(1);
expect(linkedList.toString()).toBe('');
expect(linkedList.head).toBeNull();
expect(linkedList.tail).toBeNull();
});
it('should delete node by key from linked list', () => {

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@ -0,0 +1,28 @@
import LinkedList from '../linked-list/LinkedList';
export default class Queue {
constructor() {
this.linkedList = new LinkedList();
}
isEmpty() {
return !this.linkedList.tail;
}
peek() {
if (!this.linkedList.tail) {
return null;
}
return this.linkedList.tail.value;
}
add(value) {
this.linkedList.append({ value });
}
remove() {
const removedTail = this.linkedList.deleteTail();
return removedTail ? removedTail.value : null;
}
}

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@ -0,0 +1,8 @@
# Queue
|Operation |Complexity |
|---------------------------|-------------------|
|Find |O() |
|Insert/delete at beginning |O() |
|Insert/delete in middle |O() |
|Insert/delete at end |O() |

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@ -0,0 +1,51 @@
import Queue from '../Queue';
describe('Queue', () => {
it('should create empty queue', () => {
const queue = new Queue();
expect(queue).not.toBeNull();
expect(queue.linkedList).not.toBeNull();
});
it('should add data to queue', () => {
const queue = new Queue();
queue.add(1);
queue.add(2);
expect(queue.linkedList.toString()).toBe('1,2');
});
it('should peek data from queue', () => {
const queue = new Queue();
expect(queue.peek()).toBeNull();
queue.add(1);
queue.add(2);
expect(queue.peek()).toBe(2);
expect(queue.peek()).toBe(2);
});
it('should check if queue is empty', () => {
const queue = new Queue();
expect(queue.isEmpty()).toBeTruthy();
queue.add(1);
expect(queue.isEmpty()).toBeFalsy();
});
it('should remove from empty', () => {
const queue = new Queue();
queue.add(1);
queue.add(2);
expect(queue.remove()).toBe(2);
expect(queue.remove()).toBe(1);
expect(queue.isEmpty()).toBeTruthy();
});
});