Template:Task: Difference between revisions
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<pre> |
<pre> |
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> Search Size: 1000 |
> 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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> 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. |
> 35 twin prime pairs. |
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</pre> |
</pre> |
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Revision as of 05:47, 26 July 2020
Twin primes are pairs of natural numbers(P1 and P2) that satisfy the following:
- P1 and P2 are primes
- P1 + 2 = P2
Write a program that displays the number of twin primes that can be found under a user-inputted number.
Examples below:
- Output:
> Search Size: 100 > 8 twin prime pairs.
> Search Size: 1000 > 35 twin prime pairs.