generating Variations without repetitions / Permutations in java

Question

I have to generate all variations without repetitions made of digits 0 - 9.

Length of them could be from 1 to 10. I really don\'t know how to solve it, especially ho

Answer 1

Imagine you had a magical function - given an array of digits, it will return you the correct permutations.

How can you use that function to produce a new list of permutations with just one extra digit?

e.g.,

if i gave you a function called permute_three(char[3] digits), and i tell you that it only works for digits 0, 1, 2, how can you write a function that can permute 0, 1, 2, 3, using the given permute_three function?

...

once you solved that, what do you notice? can you generalize it?