# 1759. Count Number of Homogenous Substrings

<https://leetcode.com/problems/count-number-of-homogenous-substrings>

## Description

Given a string `s`, return *the number of **homogenous** substrings of* `s`*.* Since the answer may be too large, return it **modulo** `109 + 7`.

A string is **homogenous** if all the characters of the string are the same.

A **substring** is a contiguous sequence of characters within a string.

**Example 1:**

```

**Input:** s = "abbcccaa"
**Output:** 13
**Explanation:** The homogenous substrings are listed as below:
"a"   appears 3 times.
"aa"  appears 1 time.
"b"   appears 2 times.
"bb"  appears 1 time.
"c"   appears 3 times.
"cc"  appears 2 times.
"ccc" appears 1 time.
3 + 1 + 2 + 1 + 3 + 2 + 1 = 13.
```

**Example 2:**

```

**Input:** s = "xy"
**Output:** 2
**Explanation:** The homogenous substrings are "x" and "y".
```

**Example 3:**

```

**Input:** s = "zzzzz"
**Output:** 15
```

**Constraints:**

* `1 <= s.length <= 105`
* `s` consists of lowercase letters.

## ac

```java
```