public static void main(String[] args) {
        String filename  = args[0];
        String separator = args[1];
        In in = new In(filename);

        ST<String, Queue<String>> st = new ST<String, Queue<String>>();
        ST<String, Queue<String>> ts = new ST<String, Queue<String>>();

        while (in.hasNextLine()) {
            String line = in.readLine();
            String[] fields = line.split(separator);
            String key = fields[0];
            for (int i = 1; i < fields.length; i++) {
                String val = fields[i];
                if (!st.contains(key)) st.put(key, new Queue<String>());
                if (!ts.contains(val)) ts.put(val, new Queue<String>());
                st.get(key).enqueue(val);
                ts.get(val).enqueue(key);
            }
        }

        StdOut.println("Done indexing");

        // read queries from standard input, one per line
        while (!StdIn.isEmpty()) {
            String query = StdIn.readLine();
            if (st.contains(query)) 
                for (String vals : st.get(query))
                    StdOut.println("  " + vals);
            if (ts.contains(query)) 
                for (String keys : ts.get(query))
                    StdOut.println("  " + keys);
        }

    }