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Commit 55df4d0

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Merge pull request knaxus#156 from knaxus/heaps
Heaps
2 parents a7956bd + 2c1011a commit 55df4d0

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‎.assets/dsa.jpeg‎

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‎.assets/logo.png‎

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‎README.md‎

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<img src=".assets/logo.png" align="right"/>
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# Problem Solving using Javascript
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[![Open Source Love](https://badges.frapsoft.com/os/v2/open-source.svg?v=103)](https://github.com/vinitshahdeo/HacktoberFest)
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Collection of interview questions with Unit Tests. Problems includes Data Structures, Logical and few Classical problems.
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## Table of Contents
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![DSA](.assets/dsa.jpeg)
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## Overview
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This repo contains the following sections implemented in **JavaScript**
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This repo contains the following in **JavaScript**
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- Data Structures
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- Algorithms
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- Logical Problems
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- Classics (Few of the classical questions)
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- [Data Structures](src/_DataStructures_)
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- [Algorithms](src/_Algorithms_)
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- [Logical Problems](src/_Problems_)
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- [Classics (Few of the classical questions)](src/_Classics_)
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Find the detailed Table of Contents here: [Detailed TOC](TOC.md)
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Find the detailed contents and problem list here: [Table Of Contents](TOC.md)
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## CONTRIBUTION Guide
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## Contribution Guide
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It's great to know that you want to contribute to this repo. Thanks for taking interest. please fing the [guide here](https://github.com/knaxus/problem-solving-javascript/blob/master/CONTRIBUTING.md)
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‎TOC.md‎

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## Table of Contents
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### Data Structures
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- [Unique words count in a Trie](src/_DataStructures_/Trees/Trie/unique-word-count)
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- [All the words from a Trie](src/_DataStructures_/Trees/Trie/all-words-in-trie)
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- [Unique words in a Trie](src/_DataStructures_/Trees/Trie/get-unique-words)
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- [Heaps](src/_DataStructures_/Heaps)
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- [MaxHeap](src/_DataStructures_/Heaps/MaxHeap)
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- [MinHeap](src/_DataStructures_/Heaps/MinHeap)
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- Problems
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- [K Largest Elements](src/_DataStructures_/Heaps/k-largest-in-array)
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- [K Smallest Elements](src/_DataStructures_/Heaps/k-smallest-in-array)
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### Logical Problems
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- [LRU Cache](src/_Algorithms_/lru-cache)
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- Path Finders
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- [A*](src/_Algorithms_/path-finder/a-star)
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- [A\*](src/_Algorithms_/path-finder/a-star)
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### Classics
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‎src/_DataStructures_/Heaps/MaxHeap/MaxHeap.test.js‎

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@@ -15,6 +15,11 @@ describe('MaxHeap', () => {
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expect(mh instanceof MaxHeap).toEqual(true);
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});
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it('Should create a MaxHeap using collection', () => {
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const mHBulk = new MaxHeap([1, 3, 21, 9, 101, 0]);
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expect(mHBulk.getMax()).toEqual(101);
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});
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it('Should add an element to the MaxHeap', () => {
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mh.add(10);
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expect(mh.getMax()).toEqual(10);
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expect(mh.remove()).toEqual(1);
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expect(mh.getMax()).toEqual(null);
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});
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it('Should return `null` on `remove() called on empty heap`', () => {
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expect(mh.getMax()).toEqual(null);
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});
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});

‎src/_DataStructures_/Heaps/MaxHeap/index.js‎

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class MaxHeap {
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constructor() {
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constructor(collection) {
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this.heap = [];
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if (collection) {
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collection.forEach((element) => {
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this.add(element);
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});
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}
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}
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add(element) {
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}
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getMax() {
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return this.heap[0] || null;
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return this.heap[0] !==undefined ? this.heap[0] : null;
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}
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remove() {
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const max = this.heap[0] !== undefined ? this.heap[0] : null;
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// return the element at the root
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const max = this.heap[0] || null;
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if (this.heap.length === 1) {
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this.heap.pop();
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}
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if (this.heap.length > 1) {
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// move the leaf to the root
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this.heap[0] = this.heap[this.heap.length - 1];
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this.heap.splice(this.heap.length-1,1);
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this.heap.pop();
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// restore the heapify property
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// eslint-disable-next-line no-underscore-dangle
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this.__heapify(0);
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return max;
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}
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if (this.heap.length === 1) {
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this.heap.splice(this.heap.length - 1, 1);
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return max;
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}
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return max;
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}
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const MinHeap = require('.');
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describe('MinHeap', () => {
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it('Should be a class', () => {
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expect(typeof MinHeap.prototype.constructor).toEqual('function');
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});
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const mh = new MinHeap();
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beforeEach(() => {
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mh.destroy();
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});
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it('Should create an instance of MinHeap', () => {
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expect(mh instanceof MinHeap).toEqual(true);
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});
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it('Should create a MinHeap using collection', () => {
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const mHBulk = new MinHeap([112, 3, 21, 9, 10, 0]);
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expect(mHBulk.getMin()).toEqual(0);
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});
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it('Should add an element to the MinHeap', () => {
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mh.add(10);
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expect(mh.getMin()).toEqual(10);
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});
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it('Should keep the smallest element at the root', () => {
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[12, 5, 34].forEach(el => mh.add(el));
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expect(mh.getMin()).toEqual(5);
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});
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it('Should retain Heap properties after removal of an element', () => {
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[12, 45, 1, 34].forEach(el => mh.add(el));
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expect(mh.getMin()).toEqual(1);
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mh.remove();
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expect(mh.getMin()).toEqual(12);
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});
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it('Should return `null` when heap is empty', () => {
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[1, 34].forEach(el => mh.add(el));
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expect(mh.getMin()).toEqual(1);
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mh.remove();
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mh.remove();
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expect(mh.getMin()).toEqual(null);
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});
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it('Should return the elelment value on `remove()`', () => {
49+
[1, 34].forEach(el => mh.add(el));
50+
expect(mh.getMin()).toEqual(1);
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expect(mh.remove()).toEqual(1);
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expect(mh.remove()).toEqual(34);
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expect(mh.getMin()).toEqual(null);
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});
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it('Should return `null` on `remove() called on empty heap`', () => {
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expect(mh.getMin()).toEqual(null);
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});
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});
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class MinHeap {
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constructor(collection) {
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this.heap = [];
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if (collection) {
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collection.forEach((element) => {
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this.add(element);
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});
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}
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}
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add(element) {
13+
this.heap.push(element);
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// check for the parent element & swap if required
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// eslint-disable-next-line no-underscore-dangle
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this.__traverseUpAndSwap(this.heap.length - 1);
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}
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getMin() {
20+
return this.heap[0] !== undefined ? this.heap[0] : null;
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}
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remove() {
24+
const min = this.heap[0] !== undefined ? this.heap[0] : null;
25+
if (this.heap.length === 1) {
26+
this.heap.pop();
27+
}
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if (this.heap.length > 1) {
29+
this.heap[0] = this.heap[this.heap.length - 1];
30+
this.heap.pop();
31+
// eslint-disable-next-line no-underscore-dangle
32+
this.__heapify(0);
33+
}
34+
return min;
35+
}
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destroy() {
38+
this.heap = [];
39+
}
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41+
// eslint-disable-next-line consistent-return
42+
__traverseUpAndSwap(index) {
43+
if (index <= 0) return null;
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45+
const parent = Math.floor(index / 2);
46+
47+
if (this.heap[parent] > this.heap[index]) {
48+
const temp = this.heap[parent];
49+
this.heap[parent] = this.heap[index];
50+
this.heap[index] = temp;
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// eslint-disable-next-line no-underscore-dangle
52+
this.__traverseUpAndSwap(parent);
53+
}
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}
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56+
__heapify(index) {
57+
const left = index * 2;
58+
const right = index * 2 + 1;
59+
60+
let smallest = index;
61+
62+
if (this.heap.length > left && this.heap[smallest] > this.heap[left]) {
63+
smallest = left;
64+
}
65+
if (this.heap.length > right && this.heap[smallest] > this.heap[right]) {
66+
smallest = right;
67+
}
68+
if (smallest !== index) {
69+
const tmp = this.heap[smallest];
70+
this.heap[smallest] = this.heap[index];
71+
this.heap[index] = tmp;
72+
// eslint-disable-next-line no-underscore-dangle
73+
this.__heapify(smallest);
74+
}
75+
}
76+
}
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module.exports = MinHeap;
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const MaxHeap = require('../MaxHeap');
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/**
4+
* Find the 4 largest elements from an array
5+
*/
6+
7+
function findKLargest(collection, k) {
8+
if (!collection || !Array.isArray(collection)) {
9+
throw new Error('Invalid / missing collection');
10+
}
11+
12+
// create a MaxHeap using the collection
13+
const mh = new MaxHeap(collection);
14+
const result = [];
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16+
for (let i = 0; i < k; i += 1) {
17+
result.push(mh.remove());
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}
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return result;
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}
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module.exports = findKLargest;
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/**
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* Find 4 smallest elements in an array
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*/
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const MinHeap = require('../MinHeap');
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function findKSmallest(collection, k) {
8+
if (!collection || !Array.isArray(collection)) {
9+
throw new Error('Invalid / missing collection');
10+
}
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12+
// create a MinHeap using the collection
13+
const mh = new MinHeap(collection);
14+
const result = [];
15+
for (let i = 0; i < k; i += 1) {
16+
result.push(mh.remove());
17+
}
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return result;
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}
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module.exports = findKSmallest;

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