License Key Formatting Problem


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.

Return the reformatted license key.

Example 1:

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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:

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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

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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;
    }
};




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