1698. Number of Distinct Substrings in a String
Given a string s, return the number of distinct substrings of s.
A substring of a string is obtained by deleting any number of characters (possibly zero)
from the front of the string and any number (possibly zero) from the back of the string.
Example 1:
Input: s = "aabbaba"
Output: 21
Explanation: The set of distinct strings is ["a","b","aa","bb","ab","ba","aab","abb","bba","aba","aabb","abba","bbab","baba","aabba","abbab","bbaba","aabbab","abbaba","aabbaba"]
Example 2:
Input: s = "abcdefg"
Output: 28
Constraints:
1 <= s.length <= 500
s consists of lowercase English letters.
Follow up: Can you solve this problem in O(n) time complexity?

Algorithm

Use a Trie, and every time a new Trie node created, meaning a new substring.

If O(n) time complexity, then we need some extra space to store for de-dup check, like a Set.