1694.ReformatPhoneNumber.py

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

    Example:
    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.
'''
#Difficulty: Easy
#108 / 108 test cases passed.
#Runtime: 32 ms
#Memory Usage: 14.1 MB

#Runtime: 32 ms, faster than 75.00% of Python3 online submissions for Reformat Phone Number.
#Memory Usage: 14.1 MB, less than 100.00% of Python3 online submissions for Reformat Phone Number.

class Solution:
    def reformatNumber(self, number: str) -> str:
        i = 0
        count = 0
        number = number.replace('-', '').replace(' ', '')
        number = list(number)
        while i < len(number)-1:
            i += 1
            count += 1
            if count == 3:
                number.insert(i, '-')
                i += 1
                count = 0
        if number[-2] == '-':
            number[-3], number[-2] = number[-2], number[-3]
        return ''.join(number)