Check if Strings Are Rotations of Each Other

Given two strings s1 and s2 of equal length, determine whether s2 is a rotation of s1.
A string is said to be a rotation of another if it can be obtained by shifting some leading characters of the original string to its end without changing the order of characters.

Examples:

Input: s1 = "abcd", s2 = "cdab"
Output: true
Explanation: After 2 right rotations, s1 will become equal to s2.

Input: s1 = "aab", s2 = "aba"
Output: true
Explanation: After 1 left rotation, s1 will become equal to s2.

Input: s1 = "abcd", s2 = "acbd"
Output: false
Explanation: Strings are not rotations of each other.

[Naive Approach] Generating all rotations - O(n^2) Time and O(1) Space

The idea is to generate all possible rotations of the first string and check if any of these rotations match the second string. If any rotation matches, the two strings are rotations of each other, otherwise they are not.

true

[Expected Approach] Using KMP Algorithm - O(n) Time and O(n) Space

The idea is that when a string is concatenated with itself, all possible rotations of the string will naturally appear as substrings within this concatenated string. To determine if another string is a rotation of the first, we can use KMP Algorithm to check if the second string exists as a substring in the concatenated form of the first string.

true

[Alternate Approach] Using Rabin Karp Rolling Hash - O(n) Time and O(n) Space

The idea is that when a string is concatenated with itself, all possible rotations of the string will naturally appear as substrings within this concatenated string. To do this efficiently, we use Rolling Hash (with double hashing) to compute hashes of all substrings of length n in s1 + s1, and compare them with the hash of s2.

true