total-characters-in-string-after-transformations-i

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Algorithms

You are given a string <code>s</code> and an integer <code>t</code>, representing the number of transformations to perform. In one transformation, every character in <code>s</code> is replaced according to the following rules:

<ul>
	<li>If the character is <code>&#39;z&#39;</code>, replace it with the string <code>&quot;ab&quot;</code>.</li>
	<li>Otherwise, replace it with the next character in the alphabet. For example, <code>&#39;a&#39;</code> is replaced with <code>&#39;b&#39;</code>, <code>&#39;b&#39;</code> is replaced with <code>&#39;c&#39;</code>, and so on.</li>
</ul>

Return the length of the resulting string after exactly <code>t</code> transformations.

Since the answer may be very large, return it modulo <code>109 + 7</code>.

&nbsp;
Example 1:

<div class="example-block">
Input: s = &quot;abcyy&quot;, t = 2

Output: 7

Explanation:

<ul>
	<li>First Transformation (t = 1):

	<ul>
		<li><code>&#39;a&#39;</code> becomes <code>&#39;b&#39;</code></li>
		<li><code>&#39;b&#39;</code> becomes <code>&#39;c&#39;</code></li>
		<li><code>&#39;c&#39;</code> becomes <code>&#39;d&#39;</code></li>
		<li><code>&#39;y&#39;</code> becomes <code>&#39;z&#39;</code></li>
		<li><code>&#39;y&#39;</code> becomes <code>&#39;z&#39;</code></li>
		<li>String after the first transformation: <code>&quot;bcdzz&quot;</code></li>
	</ul>
	</li>
	<li>Second Transformation (t = 2):
	<ul>
		<li><code>&#39;b&#39;</code> becomes <code>&#39;c&#39;</code></li>
		<li><code>&#39;c&#39;</code> becomes <code>&#39;d&#39;</code></li>
		<li><code>&#39;d&#39;</code> becomes <code>&#39;e&#39;</code></li>
		<li><code>&#39;z&#39;</code> becomes <code>&quot;ab&quot;</code></li>
		<li><code>&#39;z&#39;</code> becomes <code>&quot;ab&quot;</code></li>
		<li>String after the second transformation: <code>&quot;cdeabab&quot;</code></li>
	</ul>
	</li>
	<li>Final Length of the string: The string is <code>&quot;cdeabab&quot;</code>, which has 7 characters.</li>
</ul>
</div>

Example 2:

<div class="example-block">
Input: s = &quot;azbk&quot;, t = 1

Output: 5

Explanation:

<ul>
	<li>First Transformation (t = 1):

	<ul>
		<li><code>&#39;a&#39;</code> becomes <code>&#39;b&#39;</code></li>
		<li><code>&#39;z&#39;</code> becomes <code>&quot;ab&quot;</code></li>
		<li><code>&#39;b&#39;</code> becomes <code>&#39;c&#39;</code></li>
		<li><code>&#39;k&#39;</code> becomes <code>&#39;l&#39;</code></li>
		<li>String after the first transformation: <code>&quot;babcl&quot;</code></li>
	</ul>
	</li>
	<li>Final Length of the string: The string is <code>&quot;babcl&quot;</code>, which has 5 characters.</li>
</ul>
</div>

&nbsp;
Constraints:

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

lengthAfterTransformations

Total Characters in String After Transformations I

Hash Table

Math

String

Dynamic Programming

Counting

给你一个字符串 <code>s</code> 和一个整数 <code>t</code>，表示要执行的 转换 次数。每次 转换 需要根据以下规则替换字符串 <code>s</code> 中的每个字符：

<ul>
	<li>如果字符是 <code>'z'</code>，则将其替换为字符串 <code>"ab"</code>。</li>
	<li>否则，将其替换为字母表中的下一个字符。例如，<code>'a'</code> 替换为 <code>'b'</code>，<code>'b'</code> 替换为 <code>'c'</code>，依此类推。</li>
</ul>

返回 恰好 执行 <code>t</code> 次转换后得到的字符串的 长度。

由于答案可能非常大，返回其对 <code>109 + 7</code> 取余的结果。

&nbsp;

示例 1：

<div class="example-block">
输入： s = "abcyy", t = 2

输出： 7

解释：

<ul>
	<li>第一次转换 (t = 1)

	<ul>
		<li><code>'a'</code> 变为 <code>'b'</code></li>
		<li><code>'b'</code> 变为 <code>'c'</code></li>
		<li><code>'c'</code> 变为 <code>'d'</code></li>
		<li><code>'y'</code> 变为 <code>'z'</code></li>
		<li><code>'y'</code> 变为 <code>'z'</code></li>
		<li>第一次转换后的字符串为：<code>"bcdzz"</code></li>
	</ul>
	</li>
	<li>第二次转换 (t = 2)
	<ul>
		<li><code>'b'</code> 变为 <code>'c'</code></li>
		<li><code>'c'</code> 变为 <code>'d'</code></li>
		<li><code>'d'</code> 变为 <code>'e'</code></li>
		<li><code>'z'</code> 变为 <code>"ab"</code></li>
		<li><code>'z'</code> 变为 <code>"ab"</code></li>
		<li>第二次转换后的字符串为：<code>"cdeabab"</code></li>
	</ul>
	</li>
	<li>最终字符串长度：字符串为 <code>"cdeabab"</code>，长度为 7 个字符。</li>
</ul>
</div>

示例 2：

<div class="example-block">
输入： s = "azbk", t = 1

输出： 5

解释：

<ul>
	<li>第一次转换 (t = 1)

	<ul>
		<li><code>'a'</code> 变为 <code>'b'</code></li>
		<li><code>'z'</code> 变为 <code>"ab"</code></li>
		<li><code>'b'</code> 变为 <code>'c'</code></li>
		<li><code>'k'</code> 变为 <code>'l'</code></li>
		<li>第一次转换后的字符串为：<code>"babcl"</code></li>
	</ul>
	</li>
	<li>最终字符串长度：字符串为 <code>"babcl"</code>，长度为 5 个字符。</li>
</ul>
</div>

&nbsp;

提示：

<ul>
	<li><code>1 &lt;= s.length &lt;= 105</code></li>
	<li><code>s</code> 仅由小写英文字母组成。</li>
	<li><code>1 &lt;= t &lt;= 105</code></li>
</ul>