Project Euler > Problem 24 > Lexicographic permutations (Java Solution)

Problem:

A permutation is an ordered arrangement of objects. For example, 3124 is one possible permutation of the digits 1, 2, 3 and 4. If all of the permutations are listed numerically or alphabetically, we call it lexicographic order. The lexicographic permutations of 0, 1 and 2 are:

012 021 102 120 201 210

What is the millionth lexicographic permutation of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9?

Solution:

2783915460

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

public interface EulerSolution{

public String run();

}

/* 
 * Solution to Project Euler problem 24
 * By Nayuki Minase
 * 
 * http://nayuki.eigenstate.org/page/project-euler-solutions
 * https://github.com/nayuki/Project-Euler-solutions
 */


public final class p024 implements EulerSolution {
 
 public static void main(String[] args) {
  System.out.println(new p024().run());
 }
 
 
 public String run() {
  // Initialize
  int[] array = new int[10];
  for (int i = 0; i < array.length; i++)
   array[i] = i;
  
  // Permute
  for (int i = 0; i < 999999; i++) {
   if (!Library.nextPermutation(array))
    throw new AssertionError();
  }
  
  // Format output
  String ans = "";
  for (int i = 0; i < array.length; i++)
   ans += array[i];
  return ans;
 }
 
}