We shall say that 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.
The product 7254 is unusual, as the identity, 39 × 186 = 7254, containing multiplicand, multiplier, and product is 1 through 9 pandigital.
Find the sum of all products whose multiplicand/multiplier/product identity can be written as a 1 through 9 pandigital.
HINT: Some products can be obtained in more than one way so be sure to only include it once in your sum.
We first have to think about the allocation of these numbers as in what digit product are formed what two digit. If we have 2 two digit number, then, the maximum product is 99 * 99 = 9801. But, this only contains 8 digits. So, it can't even be Pandigital. How abaout 1 digit and 4 digit number? This will work along with 2, 3, 4 spread (2 digit x 3 digit = 4 digit).
So, we have two for loops: One factor that goes from a 1 digit number to 2 digit. Another factor that goes from 3 digit number to 4 digit.
Checking if a number if pandigital is pretty simple. We caa use set() function or use double for loop.
Answer: 45228
Runtime: 383 ms