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Algorithms

Alice is texting Bob using her phone. The mapping of digits to letters is shown in the figure below.
<img alt="" src="https://assets.leetcode.com/uploads/2022/03/15/1200px-telephone-keypad2svg.png" style="width: 200px; height: 162px;" />
In order to add a letter, Alice has to press the key of the corresponding digit <code>i</code> times, where <code>i</code> is the position of the letter in the key.

<ul>
	<li>For example, to add the letter <code>&#39;s&#39;</code>, Alice has to press <code>&#39;7&#39;</code> four times. Similarly, to add the letter <code>&#39;k&#39;</code>, Alice has to press <code>&#39;5&#39;</code> twice.</li>
	<li>Note that the digits <code>&#39;0&#39;</code> and <code>&#39;1&#39;</code> do not map to any letters, so Alice does not use them.</li>
</ul>

However, due to an error in transmission, Bob did not receive Alice&#39;s text message but received a string of pressed keys instead.

<ul>
	<li>For example, when Alice sent the message <code>&quot;bob&quot;</code>, Bob received the string <code>&quot;2266622&quot;</code>.</li>
</ul>

Given a string <code>pressedKeys</code> representing the string received by Bob, return the total number of possible text messages Alice could have sent.

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

&nbsp;
Example 1:

<pre>
Input: pressedKeys = &quot;22233&quot;
Output: 8
Explanation:
The possible text messages Alice could have sent are:
&quot;aaadd&quot;, &quot;abdd&quot;, &quot;badd&quot;, &quot;cdd&quot;, &quot;aaae&quot;, &quot;abe&quot;, &quot;bae&quot;, and &quot;ce&quot;.
Since there are 8 possible messages, we return 8.
</pre>

Example 2:

<pre>
Input: pressedKeys = &quot;222222222222222222222222222222222222&quot;
Output: 82876089
Explanation:
There are 2082876103 possible text messages Alice could have sent.
Since we need to return the answer modulo 109 + 7, we return 2082876103 % (109 + 7) = 82876089.
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= pressedKeys.length &lt;= 105</code></li>
	<li><code>pressedKeys</code> only consists of digits from <code>&#39;2&#39;</code> - <code>&#39;9&#39;</code>.</li>
</ul>