Template:Task: Difference between revisions
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{{infobox_begin}}{{Task/Icon}}'''{{ |
{{infobox_begin}}{{Task/Icon}}'''{{PAGENAME}}'''<includeonly>{{#set:is task=true}}</includeonly><br/> |
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You are encouraged to [[Rosetta Code:Solve a Task|solve this task]] according to the task description, using any language you may know.<includeonly>[[Category:Programming Tasks]]{{#if:{{{1|}}}|[[Category:{{{1}}}]]|[[Category:Solutions by Programming Task]]}}</includeonly>{{infobox_end}}<noinclude> |
You are encouraged to [[Rosetta Code:Solve a Task|solve this task]] according to the task description, using any language you may know.<includeonly>[[Category:Programming Tasks]]{{#if:{{{1|}}}|[[Category:{{{1}}}]]|[[Category:Solutions by Programming Task]]}}</includeonly>{{infobox_end}}<noinclude> |
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{{template|Task identifier}} |
{{template|Task identifier}} |
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<hr /> |
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A twin prime is a pair of natural numbers P1 and P2 that satisfy the following: |
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This template identifies a page as a task page and adds it to [[:Category:Programming Tasks]] and either the category identified by the first argument to the template instance or (if none is supplied) [[:Category:Solutions by Programming Task]]</noinclude> |
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1. P1 and P2 are primes |
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2. P1 + 2 = P2 |
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Write a program that displays the number of twin primes that can be found under a user-inputted number. |
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Examples below: |
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{{out}} |
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<pre> |
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> Search Size: 100 |
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> 8 twin prime pairs. |
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</pre> |
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<pre> |
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> Search Size: 1000 |
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> 35 twin prime pairs. |
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</pre> |
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=={{header|Java}}== |
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BigInteger implementation: |
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<lang Java> |
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import java.math.BigInteger; |
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import java.util.Scanner; |
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public class twinPrimes { |
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public static void main(String[] args) { |
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Scanner input = new Scanner(System.in); |
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System.out.println("Search Size: "); |
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BigInteger max = input.nextBigInteger(); |
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int counter = 0; |
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for(BigInteger x = new BigInteger("3"); x.compareTo(max) <= 0; x = x.add(BigInteger.ONE)){ |
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BigInteger sqrtNum = x.sqrt().add(BigInteger.ONE); |
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if(x.add(BigInteger.TWO).compareTo(max) <= 0) { |
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counter += findPrime(x.add(BigInteger.TWO), x.add(BigInteger.TWO).sqrt().add(BigInteger.ONE)) && findPrime(x, sqrtNum) ? 1 : 0; |
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} |
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} |
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System.out.println(counter + " twin prime pairs."); |
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} |
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public static boolean findPrime(BigInteger x, BigInteger sqrtNum){ |
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for(BigInteger divisor = BigInteger.TWO; divisor.compareTo(sqrtNum) <= 0; divisor = divisor.add(BigInteger.ONE)){ |
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if(x.remainder(divisor).compareTo(BigInteger.ZERO) == 0){ |
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return false; |
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} |
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} |
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return true; |
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} |
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} |
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</lang> |
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{{out}} |
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<pre> |
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<pre> |
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> Search Size: |
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> 100 |
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> 8 twin prime pairs. |
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</pre> |
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<pre> |
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> Search Size: |
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> 1000 |
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> 35 twin prime pairs. |
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</pre> |
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Latest revision as of 12:28, 15 October 2022
You are encouraged to solve this task according to the task description, using any language you may know.
This template identifies a page as a task page and adds it to Category:Programming Tasks and either the category identified by the first argument to the template instance or (if none is supplied) Category:Solutions by Programming Task