fsharp-learning/exercism/fsharp/difference-of-squares

Difference Of Squares

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.

Hints

For this exercise the following F# features come in handy:

• The range operator allows you to succinctly create a range of values.
• List.sumBy is a condensed format to apply a function to a list and then sum the results.

Running the tests

To run the tests, run the command dotnet test from within the exercise directory.

Autoformatting the code

F# source code can be formatted with the Fantomas tool.

After installing it with dotnet tool restore, run dotnet fantomas . to format code within the current directory.

Further information

For more detailed information about the F# track, including how to get help if you’re having trouble, please visit the exercism.io F# language page.

Source

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