52 lines
1.6 KiB
Java
52 lines
1.6 KiB
Java
|
/*
|
||
|
|
This is a Java Program to Implement Sieve Of Sundaram Algorithm. This is a program to find all primes less than a number.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/**
|
||
|
|
** Java Program to implement Sieve Of Sundaram Prime generation
|
||
|
|
**/
|
||
|
|
|
||
|
|
import java.util.Scanner;
|
||
|
|
|
||
|
|
/** Class SieveOfSundaram **/
|
||
|
|
public class SieveOfSundaram
|
||
|
|
{
|
||
|
|
/** Function to calculate all primes less than n **/
|
||
|
|
private boolean[] calcPrimes(int limit)
|
||
|
|
{
|
||
|
|
int n = limit/2;
|
||
|
|
/** initialize the sieve **/
|
||
|
|
boolean[] prime = new boolean[limit];
|
||
|
|
for (int i = 1; i < n; i++)
|
||
|
|
for (int j = i; j <= (n - i) / (2 * i + 1); j++)
|
||
|
|
prime[i + j + 2 * i * j] = true;
|
||
|
|
return prime;
|
||
|
|
}
|
||
|
|
/** Function to get all primes **/
|
||
|
|
public void getPrimes(int N)
|
||
|
|
{
|
||
|
|
boolean[] primes = calcPrimes(N);
|
||
|
|
display(primes);
|
||
|
|
}
|
||
|
|
/** Function to display all primes **/
|
||
|
|
public void display(boolean[] primes)
|
||
|
|
{
|
||
|
|
System.out.print("\nPrimes = 2 3 ");
|
||
|
|
for (int i = 2; i < primes.length/2; i++)
|
||
|
|
if (!primes[i])
|
||
|
|
System.out.print((2 * i + 1) +" ");
|
||
|
|
System.out.println();
|
||
|
|
}
|
||
|
|
/** Main function **/
|
||
|
|
public static void main (String[] args)
|
||
|
|
{
|
||
|
|
Scanner scan = new Scanner(System.in);
|
||
|
|
System.out.println("Sieve Of Sundaram Prime Algorithm Test\n");
|
||
|
|
/** Make an object of SieveOfSundaram class **/
|
||
|
|
SieveOfSundaram sos = new SieveOfSundaram();
|
||
|
|
/** Accept n **/
|
||
|
|
System.out.println("Enter number to find all primes less than the number\n");
|
||
|
|
int n = scan.nextInt();
|
||
|
|
sos.getPrimes(n);
|
||
|
|
}
|
||
|
|
}
|