42 lines
1.5 KiB
Markdown
42 lines
1.5 KiB
Markdown
# Sieve
|
|
|
|
Write a program that uses 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.
|
|
|
|
To run the tests simply run the command `go test` in the exercise directory.
|
|
|
|
If the test suite contains benchmarks, you can run these with the `-bench`
|
|
flag:
|
|
|
|
go test -bench .
|
|
|
|
For more detailed info about the Go track see the [help
|
|
page](http://help.exercism.io/getting-started-with-go.html).
|
|
|
|
## Source
|
|
|
|
Sieve of Eratosthenes at Wikipedia [view source](http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes)
|