Intelligent mobile phone password is the total number of species

Intelligent mobile phone off is a very annoying thing, because there are often some secret files, make many friends to be always on tenterhooks, can only hope that the password is not let a person break. A few days ago, sent Sili of editing received a question from a reader: in iPhone and Android systems have many possible password? This seems to be "a perfect example of mathematics in life", so the Sili of pie editorial plan immediately start calculation.

There are 10000 iPhone password
The iPhone password is one of the four digits, from 0000 to 9999 are likely to become iPhone password, the possibility of 10000. The Android system is unique, it is the "password" is a path of 3 x 3 dot matrix, this path at least between four points, up nine points of connection. Therefore, with the number of path up to A (9, 4) + A (9, 5) + A (9, 6) + A (9, 7) + A (9, 8) + A (9, 9) = 985824, looks far more than the iPhone code number. However, this is only a bound Android code number. Android password has many limitations, this analysis to Sili of school brought tremendous obstacles. After careful study, Sili of pie editorial discovery -- perhaps one of the most complex mathematical problems in real life.

There are 389112 Android password
The Android password is one route 3 × 3 lattice, the route can cross, can "go on the word", almost be equal to anything (as long as it is not the point), but there is one exception: the path is not allowed to skip the way to pass the point. For example, if from the upper left corner point connected to the upper right corner of the point, the point is automatically added to the middle path. But the trouble is, this rule is also a noteworthy places: if the middle dot is used before, so this point can be jumped over.