MyTreeSet.java

import java.util.LinkedList;
import java.util.Iterator;

public class MyTreeSet{
  MyTreeMap map = new MyTreeMap();

  public void add(String key){
    // TO BE IMPLEMENTED
    // return false;
    // add key to set
    // return true if key is new, false otherwise
    map.put(key, null);
  }

  public Iterator<String> keys(){
    // TO BE IMPLEMENTED
    // return an iterator of keys
    // return null;
    return map.keys();
  }
}