482. License Key Formatting

Posted 2021-01-18 tobeabetterpig

https://leetcode.com/problems/license-key-formatting/discuss/96528/Easy-to-understand-using-StringBuilder



class Solution {
    public String licenseKeyFormatting(String S, int K) {
        String s1 = S.replace("-", "");
        s1 = s1.toUpperCase();
        
        StringBuilder sb = new StringBuilder();
        for(int i = 0; i < s1.length(); i++){
            sb.append(s1.charAt(i));
        }
        
        int len = sb.length();
        // inserting "-" from back at every k position
        for(int i = K; i < len; i = i + K){
            sb.insert(len - i, ‘-‘);
        }
        return sb.toString();
    }
}
        
        
        
        // "5F3Z-2e-9-w", K = 4
        // "5F3Z2E9W"
        // "5F3Z-2E9W"

You are given a license key represented as a string S which consists only alphanumeric character and dashes. The string is separated into N+1 groups by N dashes.

Given a number K, we would want to reformat the strings 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 all lowercase letters should be converted to uppercase.

Given a non-empty string S and a number K, format the string according to the rules described above.

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.

 

Note:

1. The length of string S will not exceed 12,000, and K is a positive integer.
2. String S consists only of alphanumerical characters (a-z and/or A-Z and/or 0-9) and dashes(-).
3. String S is non-empty.