It seems that lots of people can solve this problem with hashing. Well, I'm using 64 bit hashing and am using sufficiently large prime p (I'm using the usual polynomial hashing i.e. s+s*p+s*p*p ...). I have tried 5 different p's and I'm always catching collisions at test 52 !!! I added code to check for collision and keep working with a different random chosen p ... and now I get TL !!!
My question is: what is the smart solution to the problem that I have? What hashing have you used?
To admins: How can you guys make solutions with random p get collisions? That's probably a really good test. I know how to build anti-hash for certain p, but I cannot imagine a test that hacks 10 random p's in a row. Good job! Or more like "my solution sucks" :)