code: public int getNumSearches(String problemID){
          if(!results.containsKey(problemID)){
              throw new UnknownIDException("Unknown problem ID " + problemID + ".");
          }
          return results.get(problemID).size();
      }
docs: Get the number of different searches that have been applied to solve the problem with the given ID.
  
  @param problemID ID of the problem
  @return number of different searches applied to solve the problem
  @throws UnknownIDException if an unknown problem ID is given