## Description

LeetCode Problem 482.

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.

Example 1:

``````1
2
3
4
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:

``````1
2
3
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 <= 10^5
• s consists of English letters, digits, and dashes ‘-‘.
• 1 <= k <= 10^4

## Sample C++ Code

``````1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
class Solution {
public:
string licenseKeyFormatting(string S, int K) {
int len = S.size();
string newS = "";

int count = 0;
for (int i = len - 1; i >= 0; i --) {
if (S[i] == '-')
continue;
if (count == K) {
newS += '-';
count = 0;
}
count ++;
newS += toupper(S[i]);
}

reverse(newS.begin(), newS.end());

return newS;
}
};
``````