public class PhonewordLister {
    private PrefixTree tree;
    public PrefixTree getTree ( ) {return tree;}

    public PhonewordLister ( ) throws IOException { }
    // this constructor should set "tree" to the prefix tree created from Knuth's word list

    public static int scrabbleScore (String w) {
	// returns Scrabble score if w is made only of letters, returns 0 otherwise
        int [ ] value = {1, 3, 3, 2, 1, 4, 2, 4, 1, 8, 5, 1, 3,
                         1, 1, 3, 10, 1, 1, 1, 1, 4, 4, 8, 4, 10};
        int sum = 0;
        for (int i = 0; i < w.length( ); i++) 
	    if ('a' <= w.charAt(i) && w.charAt(i) <= 'z') sum += value[w.charAt(i) - 'a'];
	    else if ('A' <= w.charAt(i) && w.charAt(i) <= 'Z') sum += value[w.charAt(i) - 'A'];
            else return 0;
        return sum;}

    public String [ ] list (String digits) { }
    //  This is the key method to be written by the student.
    //  The input "digits" is to be a string of five characters, each a digit in the range 2-9 or a *.
    //  If it is of this form, return an array of all phonewords that can be made from the input,
    //  in order of Scrabble score with highest score first, treating a * as a wild-card.  (Handling *'s is extra credit.)
    //  If the input is invalid, return an array of length 0. 



}