After Problem 2319.
An n-digit number is pandigital if it makes use of all the digits 1 to n exactly ONCE.
For example, the 5-digit number 15234, is 1 through 5 pandigital.
Find the number of pandigital numbers in a given interval (between xlower and xupper).
The test suite is simple here, but how to compute this number with BIG interval (pandigital number length > 7) in Cody time?
For example, between 58755 and 99899923?