how to check whether 2 strings are rotations to each other ?

Question

Given 2 strings, design a function that can check whether they are rotations to each other without making any changes on them ? The return value is boolean.

e.g ABCD, ABDC, they are not rotations. return false

ABCD, CDAB or DABC are rotations. return true.

My solution:

shift one of them to right or left one position and then compare them at each iteration. If they are not equal at all iterations, return false. Otherwise, return true.

It is O(n). Are there other more efficient solutions ? What if the contents of them cannot be changed ?

thanks

Answer 1

1. Concatenate the given string with the given string.

2. Search for the target string in the concatenated string.

Example:

Given = CDAB

After step 1, Concatenated = CDABCDAB

After step 2, Success CDABCDAB
                        ^^^^