protected internal override PuzzleState popFrontier()
{
//remove a state from the top of the fringe so that it can be searched.
PuzzleState lState = Frontier.RemoveFirst();
//add it to the list of searched states so that duplicates are recognised.
Searched.AddLast(lState);
return(lState);
}
protected internal override PuzzleState popFrontier()
{
//remove an item from the fringe to be searched
PuzzleState thisState = Frontier.First.Value;
Frontier.RemoveFirst();
//Add it to the list of searched states, so that it isn't searched again
Searched.AddLast(thisState);
return(thisState);
}