<p>Given a string <code>s</code>, return <em>the number of <strong>homogenous</strong> substrings of </em><code>s</code><em>.</em> Since the answer may be too large, return it <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>

<p>A string is <strong>homogenous</strong> if all the characters of the string are the same.</p>

<p>A <strong>substring</strong> is a contiguous sequence of characters within a string.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;abbcccaa&quot;
<strong>Output:</strong> 13
<strong>Explanation:</strong> The homogenous substrings are listed as below:
&quot;a&quot;   appears 3 times.
&quot;aa&quot;  appears 1 time.
&quot;b&quot;   appears 2 times.
&quot;bb&quot;  appears 1 time.
&quot;c&quot;   appears 3 times.
&quot;cc&quot;  appears 2 times.
&quot;ccc&quot; appears 1 time.
3 + 1 + 2 + 1 + 3 + 2 + 1 = 13.</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;xy&quot;
<strong>Output:</strong> 2
<strong>Explanation:</strong> The homogenous substrings are &quot;x&quot; and &quot;y&quot;.</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;zzzzz&quot;
<strong>Output:</strong> 15
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 10<sup>5</sup></code></li>
	<li><code>s</code> consists of lowercase letters.</li>
</ul>

class Solution:
    def countHomogenous(self, s: str) -> int:
        unique = list(set(list(s)))
        n = len(s)
        total = 0
        for char in unique:
            sub_s_lens = []
            i = 0
            while i < n:
                if s[i] == char:
                    count = 1
                    for j in range(i+1,n):
                        if s[j] != char:
                            break
                        count += 1
                    sub_s_lens.append(count)
                    i += sub_s_lens[-1]+1
                else:
                    i += 1
            for length in sub_s_lens:
                resid = length
                while resid > 0:
                    total += resid
                    resid -= 1
        return total % (10**9 + 7)
            
18300