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Your task is to, given a target word and a set of candidate words, to find the subset of the candidates that are anagrams of the target.
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Given a target word and one or more candidate words, your task is to find the candidates that are anagrams of the target.
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An anagram is a rearrangement of letters to form a new word: for example `"owns"` is an anagram of `"snow"`.
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A word is _not_ its own anagram: for example, `"stop"` is not an anagram of `"stop"`.
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The target and candidates are words of one or more ASCII alphabetic characters (`A`-`Z` and `a`-`z`).
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Lowercase and uppercase characters are equivalent: for example, `"PoTS"` is an anagram of `"sTOp"`, but `StoP` is not an anagram of `sTOp`.
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The anagram set is the subset of the candidate set that are anagrams of the target (in any order).
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Words in the anagram set should have the same letter case as in the candidate set.
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The target word and candidate words are made up of one or more ASCII alphabetic characters (`A`-`Z` and `a`-`z`).
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Lowercase and uppercase characters are equivalent: for example, `"PoTS"` is an anagram of `"sTOp"`, but `"StoP"` is not an anagram of `"sTOp"`.
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The words you need to find should be taken from the candidate words, using the same letter case.
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Given the target `"stone"` and candidates `"stone"`, `"tones"`, `"banana"`, `"tons"`, `"notes"`, `"Seton"`, the anagram set is `"tones"`, `"notes"`, `"Seton"`.
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Given the target `"stone"` and the candidate words `"stone"`, `"tones"`, `"banana"`, `"tons"`, `"notes"`, and `"Seton"`, the anagram words you need to find are `"tones"`, `"notes"`, and`"Seton"`.
A shipment of emergency supplies has arrived, but there's a problem.
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To protect from damage, the items — flashlights, first-aid kits, blankets — are packed inside boxes, and some of those boxes are nested several layers deep inside other boxes!
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To be prepared for an emergency, everything must be easily accessible in one box.
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Can you unpack all the supplies and place them into a single box, so they're ready when needed most?
Copy file name to clipboardExpand all lines: exercises/practice/sieve/.docs/instructions.md
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@@ -6,37 +6,96 @@ A prime number is a number larger than 1 that is only divisible by 1 and itself.
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For example, 2, 3, 5, 7, 11, and 13 are prime numbers.
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By contrast, 6 is _not_ a prime number as it not only divisible by 1 and itself, but also by 2 and 3.
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To use the Sieve of Eratosthenes, you first create a list of all the numbers between 2 and your given number.
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Then you repeat the following steps:
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To use the Sieve of Eratosthenes, first, write out all the numbers from 2 up to and including your given number.
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Then, follow these steps:
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1. Find the next unmarked number in your list (skipping over marked numbers).
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1. Find the next unmarked number (skipping over marked numbers).
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This is a prime number.
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2. Mark all the multiples of that prime number as **not** prime.
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You keep repeating these steps until you've gone through every number in your list.
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Repeat the steps until you've gone through every number.
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At the end, all the unmarked numbers are prime.
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~~~~exercism/note
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The tests don't check that you've implemented the algorithm, only that you've come up with the correct list of primes.
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To check you are implementing the Sieve correctly, a good first test is to check that you do not use division or remainder operations.
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The Sieve of Eratosthenes marks off multiples of each prime using addition (repeatedly adding the prime) or multiplication (directly computing its multiples), rather than checking each number for divisibility.
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The tests don't check that you've implemented the algorithm, only that you've come up with the correct primes.
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~~~~
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## Example
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Let's say you're finding the primes less than or equal to 10.
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- List out 2, 3, 4, 5, 6, 7, 8, 9, 10, leaving them all unmarked.
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- Write out 2, 3, 4, 5, 6, 7, 8, 9, 10, leaving them all unmarked.
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```text
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2 3 4 5 6 7 8 9 10
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```
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- 2 is unmarked and is therefore a prime.
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Mark 4, 6, 8 and 10 as "not prime".
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```text
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2 3 [4] 5 [6] 7 [8] 9 [10]
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↑
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```
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- 3 is unmarked and is therefore a prime.
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Mark 6 and 9 as not prime _(marking 6 is optional - as it's already been marked)_.
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```text
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2 3 [4] 5 [6] 7 [8] [9] [10]
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↑
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```
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- 4 is marked as "not prime", so we skip over it.
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```text
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2 3 [4] 5 [6] 7 [8] [9] [10]
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↑
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```
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- 5 is unmarked and is therefore a prime.
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Mark 10 as not prime _(optional - as it's already been marked)_.
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```text
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2 3 [4] 5 [6] 7 [8] [9] [10]
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↑
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```
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- 6 is marked as "not prime", so we skip over it.
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```text
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2 3 [4] 5 [6] 7 [8] [9] [10]
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↑
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```
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- 7 is unmarked and is therefore a prime.
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```text
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2 3 [4] 5 [6] 7 [8] [9] [10]
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↑
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```
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- 8 is marked as "not prime", so we skip over it.
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```text
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2 3 [4] 5 [6] 7 [8] [9] [10]
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↑
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```
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- 9 is marked as "not prime", so we skip over it.
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```text
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2 3 [4] 5 [6] 7 [8] [9] [10]
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↑
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```
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- 10 is marked as "not prime", so we stop as there are no more numbers to check.
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You've examined all numbers and found 2, 3, 5, and 7 are still unmarked, which means they're the primes less than or equal to 10.
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```text
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2 3 [4] 5 [6] 7 [8] [9] [10]
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↑
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```
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You've examined all the numbers and found that 2, 3, 5, and 7 are still unmarked, meaning they're the primes less than or equal to 10.
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