README.md

1694. Reformat Phone Number

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". 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". 

Example 4:

Input: number = "12" Output: "12" 

Example 5:

Input: number = "--17-5 229 35-39475 " Output: "175-229-353-94-75" 

Constraints:

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

Solutions (Python)

1. Solution

classSolution: defreformatNumber(self, number: str) ->str: digits=number.replace("-", "").replace(" ", "") blocks= [digits[i:i+3] foriinrange(0, len(digits), 3)] iflen(blocks[-1]) ==1: blocks[-1] =blocks[-2][2] +blocks[-1] blocks[-2] =blocks[-2][:2] return"-".join(blocks)