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482. License Key Formatting

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.

```public class LicenseKeyFormatting {
public static String licenseKeyFormatting(String S, int K) {
String[] str = S.split("-");
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i < str.length; i++) {
stringBuilder.append(str[i].toUpperCase());
}
if (stringBuilder.length() <= 0) return "";
int oth = stringBuilder.length() % K;
int count = stringBuilder.length() / K;
StringBuilder res = new StringBuilder();
if (oth == 0) {
for (int i = 0; i < count; i++) {
String temp = stringBuilder.substring(i * K, i * K + K);
res.append(temp + "-");
}
} else {
String head = stringBuilder.substring(0, oth);
res.append(head + "-");
StringBuilder stringBuilder1 = stringBuilder.delete(0, oth);
for (int i = 0; i < count; i++) {
String temp = stringBuilder1.substring(i * K, i * K + K);
res.append(temp + "-");
}

}
return res.substring(0, res.length() - 1);
}
}```

`````` public String licenseKeyFormatting(String S, int K) {
S = S.replaceAll("-", "").toUpperCase();
StringBuilder sb = new StringBuilder(S);
// Starting from the end of sb, and going backwards.
int i = sb.length() - K;
while(i > 0) {
sb.insert(i, '-');
i = i - K;
}
return sb.toString();
}``````