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Java-based LeetCode algorithm problem solutions, regularly updated

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1694\. Reformat Phone Number

Easy

You are given a phone number as a string `number`. `number` consists of digits, spaces `' '`, and/or dashes `'-'`.

You would like to reformat the phone number in a certain manner. Firstly, **remove** all spaces and dashes. Then, **group** the digits from left to right into blocks of length 3 **until** there are 4 or fewer digits. The final digits are then grouped as follows:

*   2 digits: A single block of length 2.
*   3 digits: A single block of length 3.
*   4 digits: Two blocks of length 2 each.

The blocks are then joined by dashes. Notice that the reformatting process should **never** produce any blocks of length 1 and produce **at most** two blocks of length 2.

Return _the phone number after formatting._

**Example 1:**

**Input:** number = "1-23-45 6"

**Output:** "123-456"

**Explanation:** The digits are "123456".t

Step 1: There are more than 4 digits, so group the next 3 digits. The 1st block is "123".

Step 2: There are 3 digits remaining, so put them in a single block of length 3. The 2nd block is "456".

Joining the blocks gives "123-456".

**Example 2:**

**Input:** number = "123 4-567"

**Output:** "123-45-67"

**Explanation:** The digits are "1234567".

Step 1: There are more than 4 digits, so group the next 3 digits. The 1st block is "123".

Step 2: There are 4 digits left, so split them into two blocks of length 2. The blocks are "45" and "67".

Joining the blocks gives "123-45-67".

**Example 3:**

**Input:** number = "123 4-5678"

**Output:** "123-456-78"

**Explanation:** The digits are "12345678".

Step 1: The 1st block is "123".

Step 2: The 2nd block is "456".

Step 3: There are 2 digits left, so put them in a single block of length 2. The 3rd block is "78".

Joining the blocks gives "123-456-78".

**Constraints:**

*   `2 <= number.length <= 100`
*   `number` consists of digits and the characters `'-'` and `' '`.
*   There are at least **two** digits in `number`.