Project Euler > Problem 41 > Pandigital prime (Java Solution)

Problem:

We shall say that an n-digit number is pandigital if it makes use of all the digits 1 to n exactly once. For example, 2143 is a 4-digit pandigital and is also prime.

What is the largest n-digit pandigital prime that exists?

Solution:

7652413

Code:

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

public interface EulerSolution{

public String run();

}

/* 
 * Solution to Project Euler problem 41
 * By Nayuki Minase
 * 
 * http://nayuki.eigenstate.org/page/project-euler-solutions
 * https://github.com/nayuki/Project-Euler-solutions
 */


public final class p041 implements EulerSolution {
 
 public static void main(String[] args) {
  System.out.println(new p041().run());
 }
 
 
 public String run() {
  for (int n = 9; n >= 1; n--) {
   int[] digits = new int[n];
   for (int i = 0; i < digits.length; i++)
    digits[i] = i + 1;
   
   int result = -1;
   do {
    if (Library.isPrime(toInteger(digits)))
     result = toInteger(digits);
   } while (Library.nextPermutation(digits));
   if (result != -1)
    return Integer.toString(result);
  }
  throw new RuntimeException("Not found");
 }
 
 
 private static int toInteger(int[] digits) {
  int result = 0;
  for (int x : digits)
   result = result * 10 + x;
  return result;
 }
 
}