# 0828. Count Unique Characters of All Substrings of a Given String

<https://leetcode.com/problems/count-unique-characters-of-all-substrings-of-a-given-string>

## Description

Let's define a function `countUniqueChars(s)` that returns the number of unique characters on `s`.

* For example if `s = "LEETCODE"` then `"L"`, `"T"`, `"C"`, `"O"`, `"D"` are the unique characters since they appear only once in `s`, therefore `countUniqueChars(s) = 5`.

Given a string `s`, return the sum of `countUniqueChars(t)` where `t` is a substring of s.

Notice that some substrings can be repeated so in this case you have to count the repeated ones too.

**Example 1:**

```
**Input:** s = "ABC"
**Output:** 10
**Explanation:** All possible substrings are: "A","B","C","AB","BC" and "ABC".
Evey substring is composed with only unique letters.
Sum of lengths of all substring is 1 + 1 + 1 + 2 + 2 + 3 = 10
```

**Example 2:**

```
**Input:** s = "ABA"
**Output:** 8
**Explanation:** The same as example 1, except countUniqueChars("ABA") = 1.
```

**Example 3:**

```
**Input:** s = "LEETCODE"
**Output:** 92
```

**Constraints:**

* `1 <= s.length <= 10`5
* `s` consists of uppercase English letters only.

## ac

```java
```