SieveOfEratosthenes.java

package Others;

/**
 * @author Varun Upadhyay (https://github.com/varunu28)
 */
public class SieveOfEratosthenes {

    /**
     * This method implements the Sieve of Eratosthenes Algorithm
     *
     * @param n The number till which we have to check for prime
     *          Prints all the prime numbers till n
     **/

    public static void findPrimesTillN(int n) {
        int[] arr = new int[n + 1];

        for (int i = 0; i <= n; i++) {
            arr[i] = 1;
        }

        arr[0] = arr[1] = 0;

        for (int i = 2; i <= Math.sqrt(n); i++) {
            if (arr[i] == 1) {
                for (int j = 2; i * j <= n; j++) {
                    arr[i * j] = 0;
                }
            }
        }

        for (int i = 0; i < n + 1; i++) {
            if (arr[i] == 1) {
                System.out.print(i + " ");
            }
        }

        System.out.println();
    }

    // Driver Program
    public static void main(String[] args) {
        int n = 100;

        // Prints 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 
        findPrimesTillN(n);
    }

}