Solution to Project Euler Problem 38: Pandigital multiples - Take the number 192 and multiply it by each of 1, 2, and 3: 192 × 1 = 192 192 × 2 = 384 192 × 3 = 576 By concatenating each product we get the 1 to 9 pandigital, 192384576. We will call 192384576 the concatenated product of 192 and (1,2,3) The same can be achieved by starting with 9 and multiplying by 1, 2, 3, 4, and 5, giving the pandigital, 918273645, which is the concatenated product of 9 and (1,2,3,4,5). What is the largest 1 to 9 pandigital 9-digit number that can be formed as the concatenated product of an integer with (1,2, ... , n) where n > 1?

• Java Code

package sikademy;
/**
 *
 * @author Archangel Macsika
 * Copyright (c) Sikademy. All rights reserved
 */

import java.util.Arrays;

public class SikademyEulerSolution {
	
	public String run() {
		int max = -1;
		for (int n = 2; n <= 9; n++) {
			for (int i = 1; i < pow(10, 9 / n); i++) {
				String concat = "";
				for (int j = 1; j <= n; j++)
					concat += i * j;
				if (isPandigital(concat))
					max = Math.max(Integer.parseInt(concat), max);
			}
		}
		return Integer.toString(max);
	}

	public static int pow(int x, int y) {
		if (x < 0)
			throw new IllegalArgumentException("Negative base not supported");
		if (y < 0)
			throw new IllegalArgumentException("Negative exponent");
		int z = 1;
		for (int i = 0; i < y; i++) {
			if (Integer.MAX_VALUE / z < x)
				throw new ArithmeticException("Overflow");
			z *= x;
		}
		return z;
	}
	
	private static boolean isPandigital(String s) {
		if (s.length() != 9)
			return false;
		char[] temp = s.toCharArray();
		Arrays.sort(temp);
		return new String(temp).equals("123456789");
	}

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

• Python Code

# 
# @author Archangel Macsika
# Copyright (c) Sikademy. All rights reserved.
# 

def compute():
	ans = ""
	for n in range(2, 10):
		for i in range(1, 10**(9 // n)):
			s = "".join(str(i * j) for j in range(1, n + 1))
			if "".join(sorted(s)) == "123456789":
				ans = max(s, ans)
	return ans


if __name__ == "__main__":
	print(compute())