count-number-of-homogenous-substrings

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Algorithms

Given a string <code>s</code>, return the number of homogenous substrings of <code>s</code>. Since the answer may be too large, return it modulo <code>109 + 7</code>.

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.

&nbsp;
Example 1:

<pre>
Input: s = &quot;abbcccaa&quot;
Output: 13
Explanation: 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>

Example 2:

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

Example 3:

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

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= s.length &lt;= 105</code></li>
	<li><code>s</code> consists of lowercase letters.</li>
</ul>

countHomogenous

Count Number of Homogenous Substrings

Consecutive Characters

consecutive-characters

连续字符

Number of Substrings With Only 1s

number-of-substrings-with-only-1s

仅含 1 的子串数

Sum of Subarray Ranges

sum-of-subarray-ranges

子数组范围和

Count the Number of Good Subarrays

count-the-number-of-good-subarrays

统计好子数组的数目

Math

String

给你一个字符串 <code>s</code> ，返回 <code>s</code> 中 同质子字符串 的数目。由于答案可能很大，只需返回对 <code>109 + 7</code> 取余 后的结果。

同质字符串 的定义为：如果一个字符串中的所有字符都相同，那么该字符串就是同质字符串。

子字符串 是字符串中的一个连续字符序列。

&nbsp;

示例 1：

<pre>
输入：s = "abbcccaa"
输出：13
解释：同质子字符串如下所列：
"a" 出现 3 次。
"aa" 出现 1 次。
"b" 出现 2 次。
"bb" 出现 1 次。
"c" 出现 3 次。
"cc" 出现 2 次。
"ccc" 出现 1 次。
3 + 1 + 2 + 1 + 3 + 2 + 1 = 13</pre>

示例 2：

<pre>
输入：s = "xy"
输出：2
解释：同质子字符串是 "x" 和 "y" 。</pre>

示例 3：

<pre>
输入：s = "zzzzz"
输出：15
</pre>

&nbsp;

提示：

<ul>
	<li><code>1 &lt;= s.length &lt;= 105</code></li>
	<li><code>s</code> 由小写字符串组成。</li>
</ul>