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katrinleinweber's solution

to Difference Of Squares in the R Track

Published at Jul 13 2018 · 2 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.


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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.



context("difference of squares")

test_that("difference of squares 0", {
  input <- 0
  expect_equal(difference_of_squares(input), 0)

test_that("difference of squares 5", {
  input <- 5
  expect_equal(difference_of_squares(input), 170)

test_that("difference of squares 10", {
  input <- 10
  expect_equal(difference_of_squares(input), 2640)

test_that("difference of squares 100", {
  input <- 100
  expect_equal(difference_of_squares(input), 25164150)

message("All tests passed for exercise: difference-of-squares")
difference_of_squares <- function(natural_number) {
  sum(1:natural_number)^2 - sum((1:natural_number)^2)

Community comments

Find this solution interesting? Ask the author a question to learn more.
Avatar of phisanti

We have found the same solution!

Avatar of katrinleinweber

Well, it's a centuries old calculation. Our teachers might have used the same textbooks ;-)

What can you learn from this solution?

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