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| 1 | +# Sieve |
| 2 | + |
| 3 | +Use the Sieve of Eratosthenes to find all the primes from 2 up to a given |
| 4 | +number. |
| 5 | + |
| 6 | +The Sieve of Eratosthenes is a simple, ancient algorithm for finding all |
| 7 | +prime numbers up to any given limit. It does so by iteratively marking as |
| 8 | +composite (i.e. not prime) the multiples of each prime, starting with the |
| 9 | +multiples of 2. It does not use any division or remainder operation. |
| 10 | + |
| 11 | +Create your range, starting at two and continuing up to and including the given limit. (i.e. [2, limit]) |
| 12 | + |
| 13 | +The algorithm consists of repeating the following over and over: |
| 14 | + |
| 15 | +- take the next available unmarked number in your list (it is prime) |
| 16 | +- mark all the multiples of that number (they are not prime) |
| 17 | + |
| 18 | +Repeat until you have processed each number in your range. |
| 19 | + |
| 20 | +When the algorithm terminates, all the numbers in the list that have not |
| 21 | +been marked are prime. |
| 22 | + |
| 23 | +The wikipedia article has a useful graphic that explains the algorithm: |
| 24 | +https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes |
| 25 | + |
| 26 | +Notice that this is a very specific algorithm, and the tests don't check |
| 27 | +that you've implemented the algorithm, only that you've come up with the |
| 28 | +correct list of primes. A good first test is to check that you do not use |
| 29 | +division or remainder operations (div, /, mod or % depending on the |
| 30 | +language). |
| 31 | + |
| 32 | +## Setup |
| 33 | + |
| 34 | +Go through the setup instructions for Javascript to |
| 35 | +install the necessary dependencies: |
| 36 | + |
| 37 | +[https://exercism.io/tracks/javascript/installation](https://exercism.io/tracks/javascript/installation) |
| 38 | + |
| 39 | +## Requirements |
| 40 | + |
| 41 | +Install assignment dependencies: |
| 42 | + |
| 43 | +```bash |
| 44 | +$ npm install |
| 45 | +``` |
| 46 | + |
| 47 | +## Making the test suite pass |
| 48 | + |
| 49 | +Execute the tests with: |
| 50 | + |
| 51 | +```bash |
| 52 | +$ npm test |
| 53 | +``` |
| 54 | + |
| 55 | +In the test suites all tests but the first have been skipped. |
| 56 | + |
| 57 | +Once you get a test passing, you can enable the next one by |
| 58 | +changing `xtest` to `test`. |
| 59 | + |
| 60 | + |
| 61 | +## Source |
| 62 | + |
| 63 | +Sieve of Eratosthenes at Wikipedia [http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes](http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes) |
| 64 | + |
| 65 | +## Submitting Incomplete Solutions |
| 66 | +It's possible to submit an incomplete solution so you can see how others have completed the exercise. |
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