796. Rotate String - Detailed Explanation

Complexity Analysis:

• Brute Force: O(n²) time, O(1) space.
• Optimal (Concatenation): O(n) time, O(1) space.

Edge Cases:

1. Empty Strings: ("", "") should return true (an empty string is a rotation of itself).

2. Single Character: Cases like ("a", "a") should return true, while ("a", "b") should return false.

3. Identical Strings: If s and goal are identical (and non-empty), it should return true (0 rotations needed).

Common Mistakes:

1. Not checking if lengths differ before trying rotation logic (strings of different lengths can never be rotations).

2. Implementing rotation incorrectly or not handling substring slicing properly for wrap-around.

3. Forgetting that two empty strings are considered rotations of each other.

Alternative Variations:

1. Circular Array Rotations: Similar concept but rotating an array instead of a string.
2. Rotate Right Instead of Left: The problem could be framed by rotating to the right side, which is just a minor variation.

Related Problems for Further Practice:

1. LeetCode 796 - Rotate String: This problem itself, for reference on LeetCode.

2. LeetCode 459 - Repeated Substring Pattern: Check if a string is composed of repeated substrings (also uses the trick of string concatenation).

3. LeetCode 686 - Repeated String Match: Find how many times you need to repeat a string A such that B is a substring of the repeated string.