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to Difference Of Squares in the TypeScript Track

Published at May 12 2020 · 0 comments
Test suite

Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.

The square of the sum of the first ten natural numbers is (1 + 2 + ... + 10)² = 55² = 3025.

The sum of the squares of the first ten natural numbers is 1² + 2² + ... + 10² = 385.

Hence the difference between the square of the sum of the first ten natural numbers and the sum of the squares of the first ten natural numbers is 3025 - 385 = 2640.

You are not expected to discover an efficient solution to this yourself from first principles; research is allowed, indeed, encouraged. Finding the best algorithm for the problem is a key skill in software engineering.


Go through the setup instructions for TypeScript to install the necessary dependencies:



Install assignment dependencies:

$ yarn install

Making the test suite pass

Execute the tests with:

$ yarn test

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by changing xit to it.


Problem 6 at Project Euler http://projecteuler.net/problem=6

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.


import Squares from './difference-of-squares'

describe('Squares', () => {

  describe('up to 5', () => {
    const squares = new Squares(5)

    it('gets the square of sum', () => {

    xit('gets the sum of squares', () => {

    xit('gets the difference', () => {


  describe('up to 10', () => {
    const squares = new Squares(10)

    xit('gets the square of sum', () => {

    xit('gets the sum of squares', () => {

    xit('gets the difference', () => {


  describe('up to 100', () => {
    const squares = new Squares(100)

    xit('gets the square of sum', () => {

    xit('gets the sum of squares', () => {

    xit('gets the difference', () => {


class Squares{

    constructor(private end:number){


    squareOfSum = Math.pow(Array.from(new Array(this.end),(_,index)=>index+1).reduce((acc,cur)=>acc+cur),2);

    sumOfSquares = Array.from(new Array(this.end),(_,index)=>Math.pow(index+1,2)).reduce((acc,cur)=>acc+cur);

    difference = this.squareOfSum-this.sumOfSquares;

export default Squares;

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