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
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.
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.
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.
1 <= s.length <= 105
sconsists of English letters, digits, and dashes
1 <= k <= 104
Iterate the characters from the string backward and add a ‘-‘ whenever the count is a multiple of k.
class Solution: def licenseKeyFormatting(self, s: str, k: int) -> str: s = s.replace('-', '') results =  count = 0 for c in s[::-1]: if count != 0 and count % k == 0: results.insert(0, '-') results.insert(0, c.upper()) count += 1 return "".join(results)
- Time Complexity: O(N).
- Space Complexity: O(N).