Leetcode- key formatting - simple

title ：482 Key format - Simple

subject

There is a key string S , Letters only , Figures and ‘-’（ Dashes ）. among , N individual ‘-’ Divide the string into N+1 Group .

Here's a number K, Please reformat the string , Make each group just contain K Characters . Specially , The number of characters in the first group must be less than or equal to K, But at least include 1 Characters . Between two groups, you need to use ‘-’（ Dashes ） separate , And convert all lowercase letters to uppercase letters .

Given a non empty string S And number K, Format according to the rules described above .

Example 1

 Input ：S = "5F3Z-2e-9-w", K = 4
 Output ："5F3Z-2E9W"
 explain ： character string  S  It's divided into two parts , Each part  4  Characters ;
      Be careful , Two extra dashes need to be deleted .

Example 2

 Input ：S = "2-5g-3-J", K = 2
 Output ："2-5G-3J"
 explain ： character string  S  Divided into  3  Parts of , Follow the previous rules to describe , The characters in the first part can be less than the given number , The rest are  2  Characters .

Tips

1. S The length of may be very long , Please allocate the size as needed .K As a positive integer .
2. S Only alphanumeric （a-z,A-Z,0-9） And dashes ’-’
3. S Non empty

Code Java

		public String licenseKeyFormatting(String s, int k) {
    
        StringBuilder sb = new StringBuilder(s);
        StringBuilder result = new StringBuilder();
        int count = 0;
        for (int i = sb.length() - 1; i >= 0; i --) {
    
            if (sb.charAt(i) != '-') {
    
                if (count % k == 0 && count != 0){
    
                    result.append('-');
                }
                if (sb.charAt(i) >= 'a' && sb.charAt(i) <= 'z')
                    result.append((char) (sb.charAt(i) - 32));
                else
                    result.append(sb.charAt(i));
                count ++;
            }
        }
        return result.reverse().toString();
    }