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# 1698. Number of Distinct Substrings in a String

<https://leetcode.com/problems/number-of-distinct-substrings-in-a-string>

## Description

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","bab","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?

## ac

```java
```