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Java-based LeetCode algorithm problem solutions, regularly updated

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2266\. Count Number of Texts

Medium

Alice is texting Bob using her phone. The **mapping** of digits to letters is shown in the figure below.

![](https://assets.leetcode.com/uploads/2022/03/15/1200px-telephone-keypad2svg.png)

In order to **add** a letter, Alice has to **press** the key of the corresponding digit `i` times, where `i` is the position of the letter in the key.

*   For example, to add the letter `'s'`, Alice has to press `'7'` four times. Similarly, to add the letter `'k'`, Alice has to press `'5'` twice.
*   Note that the digits `'0'` and `'1'` do not map to any letters, so Alice **does not** use them.

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

*   For example, when Alice sent the message `"bob"`, Bob received the string `"2266622"`.

Given a string `pressedKeys` 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** 10⁹ + 7.

**Example 1:**

**Input:** pressedKeys = "22233"

**Output:** 8

**Explanation:** 

The possible text messages Alice could have sent are: 

"aaadd", "abdd", "badd", "cdd", "aaae", "abe", "bae", and "ce". 

Since there are 8 possible messages, we return 8.

**Example 2:**

**Input:** pressedKeys = "222222222222222222222222222222222222"

**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.

**Constraints:**

*   1 <= pressedKeys.length <= 10⁵
*   `pressedKeys` only consists of digits from `'2'` - `'9'`.