[LeetCode]#1694. Reformat Phone Number

Environment: Python 3.8

Key technique: join, split, while

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

Analysis:

1. number=”123 4–5678"
2. replace “-” with “”
3. replace “ “ with “”
4. if n size >3, 123-. left number is 45678
5. if n size >3, 123–456-. Left number is 78
6. Return 123–456–78

Solution:

class Solution:
    def reformatNumber(self, number):
        n = "".join(number.split("-"))
        n="".join(n.split(" "))
        ans = ''
        while len(n) > 4:
            ans += n[:3] + '-'
            n = n[3:]
        if len(n) == 4:
            ans += n[:2] + '-' + n[2:]
        else:
            ans += n
        return ans

Submissions:

Reference:

https://leetcode.com/problems/reformat-phone-number/discuss/1016093/Python-really-easy-to-understand-solution