## Problem:

The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime.

There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, and 97.

How many circular primes are there below one million?

55

## Code:The solution may include methods that will be found here: Library.java .

public interface EulerSolution{

public String run();

}
/*
* Solution to Project Euler problem 35
* By Nayuki Minase
*
* http://nayuki.eigenstate.org/page/project-euler-solutions
* https://github.com/nayuki/Project-Euler-solutions
*/

public final class p035 implements EulerSolution {

public static void main(String[] args) {
System.out.println(new p035().run());
}

private static final int LIMIT = Library.pow(10, 6);

private boolean[] isPrime = Library.listPrimality(LIMIT - 1);

public String run() {
int count = 0;
for (int i = 0; i < isPrime.length; i++) {
if (isCircularPrime(i))
count++;
}
return Integer.toString(count);
}

private boolean isCircularPrime(int n) {
String s = Integer.toString(n);
for (int i = 0; i < s.length(); i++) {
if (!isPrime[Integer.parseInt(s.substring(i) + s.substring(0, i))])
return false;
}
return true;
}

}

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