56 lines
1.9 KiB
Markdown
56 lines
1.9 KiB
Markdown
# Difference Of Squares
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Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.
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The square of the sum of the first ten natural numbers is
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(1 + 2 + ... + 10)² = 55² = 3025.
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The sum of the squares of the first ten natural numbers is
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1² + 2² + ... + 10² = 385.
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Hence the difference between the square of the sum of the first
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ten natural numbers and the sum of the squares of the first ten
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natural numbers is 3025 - 385 = 2640.
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You are not expected to discover an efficient solution to this yourself from
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first principles; research is allowed, indeed, encouraged. Finding the best
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algorithm for the problem is a key skill in software engineering.
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## Getting Started
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Make sure you have read the "Guides" section of the
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[C track][c-track] on the Exercism site. This covers
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the basic information on setting up the development environment expected
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by the exercises.
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## Passing the Tests
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Get the first test compiling, linking and passing by following the [three
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rules of test-driven development][3-tdd-rules].
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The included makefile can be used to create and run the tests using the `test`
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task.
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make test
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Create just the functions you need to satisfy any compiler errors and get the
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test to fail. Then write just enough code to get the test to pass. Once you've
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done that, move onto the next test.
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As you progress through the tests, take the time to refactor your
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implementation for readability and expressiveness and then go on to the next
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test.
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Try to use standard C99 facilities in preference to writing your own
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low-level algorithms or facilities by hand.
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## Source
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Problem 6 at Project Euler [http://projecteuler.net/problem=6](http://projecteuler.net/problem=6)
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## Submitting Incomplete Solutions
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It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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[c-track]: https://exercism.io/my/tracks/c
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[3-tdd-rules]: http://butunclebob.com/ArticleS.UncleBob.TheThreeRulesOfTdd
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