Given a string s, return the longest substring of s that appears at least twice within s. The repeated occurrences may overlap. If there is no duplicated substring, return an empty string.

Note: If multiple answers have the same maximum length, returning any one of them is acceptable.

Constraints:

• $2 \leq$ s.length $\leq 3 \cdot 10^4$

• s consists of lowercase English letters.

Now, let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.