68 lines
2.5 KiB
Markdown
68 lines
2.5 KiB
Markdown
# Phone Number
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Clean up user-entered phone numbers so that they can be sent SMS messages.
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The **North American Numbering Plan (NANP)** is a telephone numbering system used by many countries in North America like the United States, Canada or Bermuda. All NANP-countries share the same international country code: `1`.
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NANP numbers are ten-digit numbers consisting of a three-digit Numbering Plan Area code, commonly known as *area code*, followed by a seven-digit local number. The first three digits of the local number represent the *exchange code*, followed by the unique four-digit number which is the *subscriber number*.
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The format is usually represented as
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```text
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(NXX)-NXX-XXXX
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```
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where `N` is any digit from 2 through 9 and `X` is any digit from 0 through 9.
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Your task is to clean up differently formatted telephone numbers by removing punctuation and the country code (1) if present.
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For example, the inputs
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- `+1 (613)-995-0253`
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- `613-995-0253`
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- `1 613 995 0253`
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- `613.995.0253`
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should all produce the output
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`6139950253`
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**Note:** As this exercise only deals with telephone numbers used in NANP-countries, only 1 is considered a valid country code.
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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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Event Manager by JumpstartLab [http://tutorials.jumpstartlab.com/projects/eventmanager.html](http://tutorials.jumpstartlab.com/projects/eventmanager.html)
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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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