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/* The Computer Language Shootout
http://shootout.alioth.debian.org/
contributed by Alkis Evlogimenos
*/
import java.util.BitSet;
public class nsievebits
{
private static int nsieve(int m, BitSet bits) {
bits.set(0, m+1);
int count = 0;
for (int i = 2; i <= m; ++i) {
if (bits.get(i)) {
for (int j = i + i; j <=m; j += i)
bits.clear(j);
++count;
}
}
return count;
}
public static String padNumber(int number, int fieldLen)
{
StringBuffer sb = new StringBuffer();
String bareNumber = "" + number;
int numSpaces = fieldLen - bareNumber.length();
for (int i = 0; i < numSpaces; i++)
sb.append(" ");
sb.append(bareNumber);
return sb.toString();
}
public static void main(String[] args)
{
int n = 2;
if (args.length > 0)
n = Integer.parseInt(args[0]);
if (n < 2)
n = 2;
int m = (1 << n) * 10000;
BitSet bits = new BitSet(m+1);
System.out.println("Primes up to " + padNumber(m, 8) + " " + padNumber(nsieve(m,bits), 8));
m = (1 << n-1) * 10000;
System.out.println("Primes up to " + padNumber(m, 8) + " " + padNumber(nsieve(m,bits), 8));
m = (1 << n-2) * 10000;
System.out.println("Primes up to " + padNumber(m, 8) + " " + padNumber(nsieve(m,bits), 8));
}
}
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