## Sunday, 12 April 2009

### PROJECT EULER #38

Link to Project Euler problem 38

Take the number 192 and multiply it by each of 1, 2, and 3:

192 x 1 = 192
192 x 2 = 384
192 x 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?

`using System;using System.Text;namespace project_euler{class Program{    static void Main()    {        //Problem 37        DateTime start = DateTime.Now;        string test = "123456789";        long max = 0;        for (int i = 1; i < 10000; i++)        {            StringBuilder sb = new StringBuilder();            for (int j = 1; j < 10; j++)            {                sb.Append(i*j);                if (sb.Length == 9)                {                    string result = sb.ToString();                    char[] c = result.ToCharArray();                    Array.Sort(c);                    string s = new string(c);                    if (s == test)                        max = int.Parse(result) > max                                  ? int.Parse(result)                                  : max;                }            }        }        Console.WriteLine(max);        TimeSpan time = DateTime.Now - start;        Console.WriteLine("This took {0}", time);        Console.ReadKey();    }}}`