init impl

Author: freemanzhang

src/string/LicenseKeyFormatting.java

@@ -0,0 +1,48 @@
+package string;
+
+/*
+Now you are given a string S, which represents a software license key which we would like to format. The string S is composed of alphanumerical characters and dashes. 
+The dashes split the alphanumerical characters within the string into groups. (i.e. if there are M dashes, the string is split into M+1 groups). The dashes in the given string are possibly misplaced.
+
+We want each group of characters to be of length K (except for possibly the first group, which could be shorter, but still must contain at least one character). 
+To satisfy this requirement, we will reinsert dashes. Additionally, all the lower case letters in the string must be converted to upper case.
+
+So, you are given a non-empty string S, representing a license key to format, and an integer K. And you need to return the license key formatted according to the description above.
+
+Example 1:
+Input: S = "2-4A0r7-4k", K = 4
+
+Output: "24A0-R74K"
+
+Explanation: The string S has been split into two parts, each part has 4 characters.
+Example 2:
+Input: S = "2-4A0r7-4k", K = 3
+
+Output: "24-A0R-74K"
+
+Explanation: The string S has been split into three parts, each part has 3 characters except the first part as it could be shorter as said above.
+Note:
+The length of string S will not exceed 12,000, and K is a positive integer.
+String S consists only of alphanumerical characters (a-z and/or A-Z and/or 0-9) and dashes(-).
+String S is non-empty.
+ * */
+
+public class LicenseKeyFormatting
+{
+	public String licenseKeyFormatting( String S, int K )
+	{
+		StringBuilder result = new StringBuilder();
+		for ( int i = S.length() - 1; i >= 0; i-- )
+		{
+			if ( S.charAt( i ) != '-' )
+			{
+				if ( result.length() % ( K + 1 ) == K )
+				{
+					result.append( '-' );
+				}
+				result.append( S.charAt( i ) );
+			}
+		}
+		return result.reverse().toString().toUpperCase();
+	}
+}