Possible Duplicate:
Combination of smartphones' pattern password
I just came across with this interesting question from my colleague. I'm trying now, but meanwhile i thouht i could share here.
With the password grid shown in android home screen, how many valid passwords are possible? min password length: 4 max: 9 (correct me if i'm wrong)
I'm looking for math approach, rather eliminating invalid combinations from all combinations.
Thanks.