diff --git a/exercises/practice/sieve/.docs/instructions.md b/exercises/practice/sieve/.docs/instructions.md index 7228737a2..ec14620ce 100644 --- a/exercises/practice/sieve/.docs/instructions.md +++ b/exercises/practice/sieve/.docs/instructions.md @@ -1,30 +1,28 @@ # Instructions -Use the Sieve of Eratosthenes to find all the primes from 2 up to a given -number. +Your task is to create a program that implements the Sieve of Eratosthenes algorithm to find prime numbers. -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. It does not use any division or remainder operation. +A prime number is a number that is only divisible by 1 and itself. +For example, 2, 3, 5, 7, 11, and 13 are prime numbers. -Create your range, starting at two and continuing up to and including the given limit. (i.e. [2, limit]) +The Sieve of Eratosthenes is an ancient algorithm that works by taking a list of numbers and crossing out all the numbers that aren't prime. -The algorithm consists of repeating the following over and over: +A number that is **not** prime is called a "composite number". -- take the next available unmarked number in your list (it is prime) -- mark all the multiples of that number (they are not prime) +To use the Sieve of Eratosthenes, you first create a list of all the numbers between 2 and your given number. +Then you repeat the following steps: -Repeat until you have processed each number in your range. +1. Find the next unmarked number in your list. This is a prime number. +2. Mark all the multiples of that prime number as composite (not prime). -When the algorithm terminates, all the numbers in the list that have not -been marked are prime. +You keep repeating these steps until you've gone through every number in your list. +At the end, all the unmarked numbers are prime. -The wikipedia article has a useful graphic that explains the algorithm: -https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes +```exercism/note +[Wikipedia's Sieve of Eratosthenes article][eratosthenes] has a useful graphic that explains the algorithm. -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. A good first test is to check that you do not use -division or remainder operations (div, /, mod or % depending on the -language). +The tests don't check that you've implemented the algorithm, only that you've come up with the correct list of primes. +A good first test is to check that you do not use division or remainder operations. + +[eratosthenes]: https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes +``` diff --git a/exercises/practice/sieve/.docs/introduction.md b/exercises/practice/sieve/.docs/introduction.md new file mode 100644 index 000000000..f6c1cf79a --- /dev/null +++ b/exercises/practice/sieve/.docs/introduction.md @@ -0,0 +1,7 @@ +# Introduction + +You bought a big box of random computer parts at a garage sale. +You've started putting the parts together to build custom computers. + +You want to test the performance of different combinations of parts, and decide to create your own benchmarking program to see how your computers compare. +You choose the famous "Sieve of Eratosthenes" algorithm, an ancient algorithm, but one that should push your computers to the limits.