Question

Suppose I have the following array:

1, 4, 5, 2, 3

I need to rearrange it to

5, 1, 4, 2, 3

There is only on extra space; one int.

I figured one solution to solve it. But it is O(n^2) complexity.

Can anyone offer a faster solution?

Thanks

Edited:
sorry, not rotating array.

I need to change original array to result array.
The order can be arbitrary.
I just need to make A -> B.
B is been told to me.

thanks

Edited 2″

Make it clearer.
Array B is not fixed.
We need to find a general solution for this.

Updated:

Thank you all. Seems like this is a brain teaser question. haha 😀

My friend been asked by Amazon interviewer for this. LOL

Answer 1

This solution works using O(1) space.

>>> def arrayswap(source, dest):
...     for i in range(len(dest)):
...         source[source.index(dest[i])], source[i] = source[i], source[source.index(dest[i])]
... 
>>> a = [1, 4, 5, 2, 3]
>>> b = [5, 1, 4, 2, 3]
>>> arrayswap(a, b)
>>> a
[5, 1, 4, 2, 3]

Without using python’s tuple packing, the value of one of source[i] or source[source.index(dest[i])] could be stored in an int.