[LeetCode] 482. License Key Formatting_Easy tag: String

You are given a license key represented as a string s that consists of only alphanumeric characters and dashes. The string is separated into n + 1 groups by n dashes. You are also given an integer k.

We want to reformat the string s such that each group contains exactly k characters, except for the first group, which could be shorter than k but still must contain at least one character. Furthermore, there must be a dash inserted between two groups, and you should convert all lowercase letters to uppercase.

Return the reformatted license key.

 

Example 1:

Input: s = "5F3Z-2e-9-w", k = 4
Output: "5F3Z-2E9W"
Explanation: The string s has been split into two parts, each part has 4 characters.
Note that the two extra dashes are not needed and can be removed.

Example 2:

Input: s = "2-5g-3-J", k = 2
Output: "2-5G-3J"
Explanation: The string s has been split into three parts, each part has 2 characters except the first part as it could be shorter as mentioned above.

 

Constraints:

• 1 <= s.length <= 105
• s consists of English letters, digits, and dashes '-'.
• 1 <= k <= 104

 

Code:

class Solution:
    def licenseKeyFormatting(self, s: str, k: int) -> str:
        s = s.replace('-', '').upper()
        n = len(s)
        times, rem = divmod(n, k)
        first_group= [s[:rem]] if rem else []
        start = rem
        for _ in range(times):
            first_group.append( s[start:k + start])
            start = start + k
        return '-'.join(first_group)