/**
  * Add distribution set 'newSet' to state s (which must exist). Distribution set is only actually
  * added if it does not already exists for state s. (Assuming 'allowDupes' flag is not enabled.)
  * Returns the index of the (existing or newly added) set. Returns -1 in case of error.
  */
 public int addDistributionSet(int s, DistributionSet newSet) {
   ArrayList<DistributionSet> set;
   // Check state exists
   if (s >= numStates || s < 0) return -1;
   // Add distribution set (if new)
   set = trans.get(s);
   if (!allowDupes) {
     int i = set.indexOf(newSet);
     if (i != -1) return i;
   }
   set.add(newSet);
   // Update stats
   numDistrSets++;
   maxNumDistrSets = Math.max(maxNumDistrSets, set.size());
   numDistrs += newSet.size();
   maxNumDistrs = Math.max(maxNumDistrs, newSet.size());
   for (Distribution distr : newSet) numTransitions += distr.size();
   return set.size() - 1;
 }
 @Override
 public void clearState(int i) {
   // Do nothing if state does not exist
   if (i >= numStates || i < 0) return;
   // Clear data structures and update stats
   List<DistributionSet> list = trans.get(i);
   numDistrSets -= list.size();
   for (DistributionSet set : list) {
     numDistrs -= set.size();
     for (Distribution distr : set) numTransitions -= distr.size();
   }
   // TODO: recompute maxNumDistrSets
   // TODO: recompute maxNumDistrs
   // Remove all distribution sets
   trans.set(i, new ArrayList<DistributionSet>(0));
 }