/* * Solution to Project Euler problem 24 * Copyright (c) Project Nayuki. All rights reserved. * * https://www.nayuki.io/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()); } /* * We initialize an array as the lowest permutation of the given digits, which is the sequence * (0,1,2,3,4,5,6,7,8,9). Then we call the next permutation algorithm on it 999 999 times * (because the index in the problem is 1-based), and stringify the resulting sequence. * * The next permutation algorithm is well-known and a bit long to explain. * See: https://www.nayuki.io/page/next-lexicographical-permutation-algorithm */ 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; } }