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Commit ebf7cbb

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add merge sort
1 parent 6052715 commit ebf7cbb

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6 files changed

+231
-4
lines changed

6 files changed

+231
-4
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‎README.md

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Feel free to navigate around.
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#### Data Structures
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[Linked list](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/data-structures/linked-list.js)
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[Queue](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/data-structures/queue.js)
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[Stack](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/data-structures/stack.js)
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[Binary Search Tree](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/data-structures/binary-search-tree.js)
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#### Sorting
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[Insertion sort](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/sorting/insertion-sort.js)
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[Selection sort](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/sorting/selection-sort.js)
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[Merge sort](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/sorting/selection-sort.js)
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[Quick sort](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/sorting/selection-sort.js)
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#### Searching
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[Binary search](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/searching/binary-search.js)
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[Binary search](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/searching/binary-search.js)
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[Breadth-first search](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/searching/breadth-first-search.js)
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[Depth-first search](https://github.com/estevanmaito/algorithms-in-javascript/tree/master/searching/depth-first-search.js)

‎data-structures/linked-list.js

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// https://en.wikipedia.org/wiki/Linked_list
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function Node(data) {
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this.data = data
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this.next = null
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}
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function LinkedList() {
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this.length = 0
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this.head = null
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}
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LinkedList.prototype.add = function (value) {
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let node = new Node(value)
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current = this.head
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if (!current) {
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this.head = node
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} else {
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while (current.next) current = current.next
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current.next = node
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}
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this.length++
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return node
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}
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LinkedList.prototype.findAt = function (position) {
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if (position > -1 && position < this.length) {
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let current = this.head
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for (let i = 0; i++ < position; current = current.next);
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return current.data
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}
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return null
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}
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LinkedList.prototype.remove = function (position) {
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if (position > -1 && position < this.length) {
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let current = this.head
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if (position === 0) {
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current = current.next
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} else {
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let i = 0
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let previous
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while (i++ < position) {
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previous = current
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current = current.next
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}
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previous.next = current.next
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}
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this.length--
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return current.data
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}
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return null
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}
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const test = require('tape')
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test('Linked list add', assert => {
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let ll = new LinkedList()
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ll.add('Hello world!')
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assert.deepEqual(ll.head.data, 'Hello world!')
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assert.deepEqual(ll.length, 1)
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ll.add('Can you see me?')
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assert.deepEqual(ll.length, 2)
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assert.end()
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})
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test('Linked list findAt', assert => {
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let ll = new LinkedList()
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ll.add('Hello world!')
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ll.add('Can you see me?')
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ll.add('Now you don\'t')
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assert.deepEqual(ll.findAt(2), 'Now you don\'t')
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assert.deepEqual(ll.findAt(0), 'Hello world!')
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assert.deepEqual(ll.findAt(3), null)
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assert.end()
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})
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test('Linked list remove', assert => {
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let ll = new LinkedList()
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ll.add('Hello world!')
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ll.add('Can you see me?')
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ll.add('Now you don\'t')
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ll.remove(2)
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assert.deepEqual(2, ll.length)
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ll.remove(1)
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assert.deepEqual(1, ll.length)
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assert.end()
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})

‎data-structures/queue.js

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// https://en.wikipedia.org/wiki/Queue_(abstract_data_type)
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function Queue() {
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this.front = 0
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this.rear = 0
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this.items = {}
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}
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Queue.prototype.size = function () {
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return this.rear - this.front
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}
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Queue.prototype.enqueue = function (value) {
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this.items[this.rear++] = value
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}
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Queue.prototype.dequeue = function () {
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if (this.rear === this.front) return undefined
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let front = this.items[this.front]
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delete this.items[this.front++]
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return front
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}
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const test = require('tape')
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test('Queue enqueue', assert => {
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let q = new Queue()
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assert.deepEqual(q.dequeue(), undefined)
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q.enqueue(1)
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q.enqueue(3)
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assert.deepEqual(q.size(), 2)
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assert.deepEqual(q.dequeue(), 1)
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assert.deepEqual(q.size(), 1)
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q.enqueue(4)
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q.enqueue(5)
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assert.deepEqual(q.size(), 3)
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assert.deepEqual(q.dequeue(), 3)
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assert.deepEqual(q.size(), 2)
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assert.deepEqual(q.dequeue(), 4)
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assert.deepEqual(q.dequeue(), 5)
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assert.deepEqual(q.dequeue(), undefined)
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q.enqueue(1)
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q.enqueue(2)
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assert.deepEqual(q.dequeue(), 1)
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assert.end()
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})

‎data-structures/stack.js

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// https://en.wikipedia.org/wiki/Stack_(abstract_data_type)
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function Stack() {
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this.length = 0
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this.items = {}
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}
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Stack.prototype.push = function (value) {
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this.items[this.length++] = value
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}
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Stack.prototype.pop = function () {
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if (this.length === 0) return undefined
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let top = this.items[--this.length]
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delete this.items[this.length]
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return top
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}
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const test = require('tape')
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test('Stack add', assert => {
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let s = new Stack()
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s.push(1)
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s.push(3)
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assert.deepEqual(s.length, 2)
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assert.deepEqual(s.pop(), 3)
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assert.deepEqual(s.length, 1)
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assert.deepEqual(s.pop(), 1)
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assert.deepEqual(s.pop(), undefined)
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s.push(2)
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assert.deepEqual(s.length, 1)
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assert.end()
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})

‎searching/binary-search.js

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// https://en.wikipedia.org/wiki/Binary_search_algorithm
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let binarySearch = (targetValue, array ) => {
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let start = 0
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letend = array.length - 1
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let middle
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let start = 0,
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end = array.length - 1,
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middle
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while (start <= end) {
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middle = Math.floor((start + end) / 2)

‎sorting/merge-sort.js

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// https://en.wikipedia.org/wiki/Merge_sort
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let merge = (left, right) => {
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let arr = [],
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i = 0,
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j = 0
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while (i < left.length && j < right.length) {
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if (left[i] < right[j]) arr.push(left[i++])
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else arr.push(right[j++])
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}
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return arr.concat(left.slice(i)).concat(right.slice(j))
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}
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let mergeSort = (arr) => {
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if (arr.length > 1) {
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let middle = Math.floor(arr.length / 2),
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left = mergeSort(arr.slice(0, middle)),
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rigth = mergeSort(arr.slice(middle))
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return merge(left, rigth)
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}
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return arr
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}
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const test = require('tape')
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test('Merge sort', assert => {
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assert.deepEqual(mergeSort([2,4,5,7,1,2,3,6]), [1,2,2,3,4,5,6,7])
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assert.deepEqual(mergeSort([2,22,5,-3,4,9,3,6]), [-3,2,3,4,5,6,9,22])
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assert.deepEqual(mergeSort([]), [])
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assert.deepEqual(mergeSort([1]), [1])
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assert.end()
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})

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