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{{task|Twin Prime Conjecture}}[[Category:Primes]]{{requires|Input}} |
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{{infobox_begin}}{{Task/Icon}}{{#set:is task=true}}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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# P1 and P2 are primes |
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# P1 + 2 = P2 |
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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. |
Write a program that displays the number of twin primes that can be found under a user-inputted number. |
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> Search Size: |
> Search Size: |
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Revision as of 05:43, 26 July 2020
Template loop detected: Template:Task
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.
Java
BigInteger implementation: <lang Java> import java.math.BigInteger; import java.util.Scanner;
public class twinPrimes {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Search Size: ");
BigInteger max = input.nextBigInteger();
int counter = 0;
for(BigInteger x = new BigInteger("3"); x.compareTo(max) <= 0; x = x.add(BigInteger.ONE)){
BigInteger sqrtNum = x.sqrt().add(BigInteger.ONE);
if(x.add(BigInteger.TWO).compareTo(max) <= 0) {
counter += findPrime(x.add(BigInteger.TWO), x.add(BigInteger.TWO).sqrt().add(BigInteger.ONE)) && findPrime(x, sqrtNum) ? 1 : 0;
}
}
System.out.println(counter + " twin prime pairs.");
}
public static boolean findPrime(BigInteger x, BigInteger sqrtNum){
for(BigInteger divisor = BigInteger.TWO; divisor.compareTo(sqrtNum) <= 0; divisor = divisor.add(BigInteger.ONE)){
if(x.remainder(divisor).compareTo(BigInteger.ZERO) == 0){
return false;
}
}
return true;
}
} </lang>
- Output:
> Search Size: > 100 > 8 twin prime pairs.
> Search Size: > 1000 > 35 twin prime pairs.
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.
Java
BigInteger implementation: <lang Java> import java.math.BigInteger; import java.util.Scanner;
public class twinPrimes {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Search Size: ");
BigInteger max = input.nextBigInteger();
int counter = 0;
for(BigInteger x = new BigInteger("3"); x.compareTo(max) <= 0; x = x.add(BigInteger.ONE)){
BigInteger sqrtNum = x.sqrt().add(BigInteger.ONE);
if(x.add(BigInteger.TWO).compareTo(max) <= 0) {
counter += findPrime(x.add(BigInteger.TWO), x.add(BigInteger.TWO).sqrt().add(BigInteger.ONE)) && findPrime(x, sqrtNum) ? 1 : 0;
}
}
System.out.println(counter + " twin prime pairs.");
}
public static boolean findPrime(BigInteger x, BigInteger sqrtNum){
for(BigInteger divisor = BigInteger.TWO; divisor.compareTo(sqrtNum) <= 0; divisor = divisor.add(BigInteger.ONE)){
if(x.remainder(divisor).compareTo(BigInteger.ZERO) == 0){
return false;
}
}
return true;
}
} </lang>
- Output:
> Search Size: > 100 > 8 twin prime pairs.
> Search Size: > 1000 > 35 twin prime pairs.