private static ArrayList<T3Board> directlyReachableStates(T3Board board) {
ArrayList<T3Board> drs = new ArrayList<T3Board>();
// look for reachable states
for (int row = 1; row <= 3; row++) {
for (int col = 1; col <= 3; col++) {
T3Board next = new T3Board(board);
// if space is available, mark it
if (next.markSpace(row, col, T3Board.X)) {
// switch X and O in next stage, so the agent is always X
next.switchSeats();
// add it to the list
drs.add(next);
}
}
}
return drs;
}
private static int visitAllReachableStates(final T3Board board, final ArrayList<T3Board> states) {
states.add(board);
int leaves = 0;
if (!board.isTerminal()) {
// look for reachable states
for (T3Board next : directlyReachableStates(board))
leaves += visitAllReachableStates(next, states);
return leaves;
} else {
return 1;
}
}
public static void main(String[] args) throws IOException {
ArrayList<T3Board> states = new ArrayList<T3Board>();
int leaves = visitAllReachableStates(new T3Board(), states);
System.out.println("Leaf nodes in game tree: " + leaves);
System.out.println("Branches in game tree: " + states.size());
HashSet<String> unique = new HashSet<String>();
for (T3Board state : states) unique.add(state.toString());
System.out.println("Unique reachable states: " + unique.size());
HashSet<T3Board> reduced = new HashSet<T3Board>();
for (T3Board board : states)
if (!board.isTerminal()) reduced.add(new T3Board(board.lowestEquivalentBoard()));
System.out.println("Reduced states: " + reduced.size());
int saPairs = countStatesAndActions(reduced);
System.out.println("Reduced state-action pairs: " + saPairs);
System.out.println();
System.out.println("Small sample of reduced states");
System.out.println();
Random random = new Random();
T3Board check = null;
File statespace = new File("output/t3statespace");
if (statespace.exists()) statespace.delete();
statespace.getParentFile().mkdirs();
FileWriter out = new FileWriter(statespace);
for (T3Board board : reduced) {
out.write(board.toString() + "\n");
if (random.nextDouble() < 0.005) {
System.out.println(board.toGlyph());
check = board;
}
}
out.close();
System.out.println("Symmetry check of last sample");
System.out.println();
for (String sym : check.equivalentBoards()) {
System.out.println((new T3Board(sym)).toGlyph());
}
}