花花酱 LeetCode 1316. Distinct Echo Substrings

Return the number of distinct non-empty substrings of text that can be written as the concatenation of some string with itself.

Example 1:

Input: text = "abcabcabc"
Output: 3
Explanation: The 3 substrings are "abcabc", "bcabca" and "cabcab".

Example 2:

Input: text = "leetcodeleetcode"
Output: 2
Explanation: The 2 substrings are "ee" and "leetcodeleetcode".

Constraints:

• 1 <= text.length <= 2000
• text has only lowercase English letters.

Solution 1: Brute Force + HashSet

Try all possible substrings

Time complexity: O(n^3)
Space complexity: O(n^2)