0482. License Key Formatting

https://leetcode.com/problems/license-key-formatting

Description

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

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