public static void main(String[] args) {

        // build symbol table from standard input
        TrieST<Integer> st = new TrieST<Integer>();
        for (int i = 0; !StdIn.isEmpty(); i++) {
            String key = StdIn.readString();
            st.put(key, i);
        }

        // print results
        if (st.size() < 100) {
            StdOut.println("keys(\"\"):");
            for (String key : st.keys()) {
                StdOut.println(key + " " + st.get(key));
            }
            StdOut.println();
        }

        StdOut.println("longestPrefixOf(\"shellsort\"):");
        StdOut.println(st.longestPrefixOf("shellsort"));
        StdOut.println();

        StdOut.println("keysWithPrefix(\"shor\"):");
        for (String s : st.keysWithPrefix("shor"))
            StdOut.println(s);
        StdOut.println();

        StdOut.println("keysThatMatch(\".he.l.\"):");
        for (String s : st.keysThatMatch(".he.l."))
            StdOut.println(s);
    }