Are we officially math warriors now? :C

I found most of the answers repeatedly testing numbers, be it in std::string or math. e.g:

when found out 45690 contains 5, it will be best to test 46000 next, not 45691,
for negative numbers, rather than testing -533 after -534, jumping straight to -499 will be faster.

I made my solution an implementation of this jumping forward idea(pure math), it workded but I still felt it was not optimal.

Anybody wants to share a better mathmatical way to solve this? Thank you :D

This one is truly masterpiece

loled @ "Omae wa mo shindeiru"

Just wondering how should we make it work in python3?

Thanks :D works now

The random tests in the ruby version have some wierd rounding problem :C or is it just I missed something?

error in the 3rd test: should be n4 rather than n2