www.mikescher.com/www/statics/euler/Euler_Problem-032_explanation.md

The main focus here was optimizing the pandigital testing. The rest is just looping over every possible number.
We can optimize the outer loop a little bit if we look at the possible multiplicands. There are only 2 possibilities if we need 9 digits in our calculation:

• 1-digit number * 4-digit number = 4-digit number
• 2-digit number * 3-digit number = 4-digit number