path: root/c/difference-of-squares/README.md



# 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.

## Getting Started

Make sure you have read the "Guides" section of the
[C track][c-track] on the Exercism site. This covers
the basic information on setting up the development environment expected
by the exercises.

## Passing the Tests

Get the first test compiling, linking and passing by following the [three
rules of test-driven development][3-tdd-rules].

The included makefile can be used to create and run the tests using the `test`
task.

    make test

Create just the functions you need to satisfy any compiler errors and get the
test to fail. Then write just enough code to get the test to pass. Once you've
done that, move onto the next test.

As you progress through the tests, take the time to refactor your
implementation for readability and expressiveness and then go on to the next
test.

Try to use standard C99 facilities in preference to writing your own
low-level algorithms or facilities by hand.

## Source

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

[c-track]: https://exercism.io/my/tracks/c
[3-tdd-rules]: http://butunclebob.com/ArticleS.UncleBob.TheThreeRulesOfTdd
# 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.

## Getting Started

Make sure you have read the "Guides" section of the
[C track][c-track] on the Exercism site. This covers
the basic information on setting up the development environment expected
by the exercises.

## Passing the Tests

Get the first test compiling, linking and passing by following the [three
rules of test-driven development][3-tdd-rules].

The included makefile can be used to create and run the tests using the `test`
task.

    make test

Create just the functions you need to satisfy any compiler errors and get the
test to fail. Then write just enough code to get the test to pass. Once you've
done that, move onto the next test.

As you progress through the tests, take the time to refactor your
implementation for readability and expressiveness and then go on to the next
test.

Try to use standard C99 facilities in preference to writing your own
low-level algorithms or facilities by hand.

## Source

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

[c-track]: https://exercism.io/my/tracks/c
[3-tdd-rules]: http://butunclebob.com/ArticleS.UncleBob.TheThreeRulesOfTdd