LeetCode_482. License Key Formatting

482. License Key Formatting

Easy

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.

package leetcode.easy;

public class LicenseKeyFormatting {
	public String licenseKeyFormatting(String S, int K) {
		StringBuffer sb = new StringBuffer();
		int count = 0;
		for (int i = S.length() - 1; i >= 0; i--) {
			char c = S.charAt(i);
			if (c != '-') {
				if (count > 0 && count % K == 0) {
					sb.append('-');
				}
				sb.append(c);
				count++;
			}
		}
		return sb.reverse().toString().toUpperCase();
	}

	@org.junit.Test
	public void test() {
		System.out.println(licenseKeyFormatting("5F3Z-2e-9-w", 4));
		System.out.println(licenseKeyFormatting("2-5g-3-J", 2));
	}
}