Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.
The Sieve of Eratosthenes is a simple, ancient algorithm for finding all prime numbers up to any given limit. It does so by iteratively marking as composite (i.e. not prime) the multiples of each prime, starting with the multiples of 2.
Create your range, starting at two and continuing up to and including the given limit. (i.e. [2, limit])
The algorithm consists of repeating the following over and over:
- take the next available unmarked number in your list (it is prime)
- mark all the multiples of that number (they are not prime)
Repeat until you have processed each number in your range.
When the algorithm terminates, all the numbers in the list that have not been marked are prime.
The wikipedia article has a useful graphic that explains the algorithm: https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
Notice that this is a very specific algorithm, and the tests don't check that you've implemented the algorithm, only that you've come up with the correct list of primes.
Running the tests
To run the tests run the command
go test from within the exercise directory.
If the test suite contains benchmarks, you can run these with the
go test -bench .
Keep in mind that each reviewer will run benchmarks on a different machine, with different specs, so the results from these benchmark tests may vary.
For more detailed information about the Go track, including how to get help if you're having trouble, please visit the exercism.io Go language page.
Sieve of Eratosthenes at Wikipedia http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.