I had a scan of the code examples, but one other idea that occurred to me is that you could immediately drop any numbers below 999 (probably slightly higher, but that would need calculation rather than being intuitive).
> probably slightly higher, but that would need calculation rather than being intuitive
I think it’s easy to figure out that 3999 is the smallest positive integer whose decimal digits add up to 30 (can’t get there with 3 digits, and for 4, you want the first digit to be as small as possible. You get that by making the other 3 as high as possible)
