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1694. Reformat Phone Number

Difficulty Topics

Description

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".

 

Constraints:

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

Solution

reformat-phone-number.py
class Solution:
    def reformatNumber(self, number: str) -> str:
        number = number.replace("-","").replace(" ", "")

        n = len(number)
        i = 0
        res = []
        while n > 4:
            res.append(number[i:i+3])
            i += 3
            n -= 3

        if n == 4:
            res.append(number[i:i+2])
            res.append(number[i+2:i+4])
        else:
            res.append(number[i:])

        return "-".join(res)