public int min(final Board board, final int depth) {
if (depth == 0 || isEndGameScenario(board)) {
return this.evaluator.evaluate(board, depth);
}
int lowestSeenValue = Integer.MAX_VALUE;
for (final Move move : board.currentPlayer().getLegalMoves()) {
final MoveTransition moveTransition = board.currentPlayer().makeMove(move);
if (moveTransition.getMoveStatus().isDone()) {
final int currentValue = max(moveTransition.getTransitionBoard(), depth - 1);
if (currentValue <= lowestSeenValue) {
lowestSeenValue = currentValue;
}
}
}
return lowestSeenValue;
}
private List<Move> orderImpl(final Board board, final int depth) {
final List<MoveOrderEntry> moveOrderEntries = new ArrayList<>();
final boolean SORT_DESCENDING = board.currentPlayer().getColor().isWhite();
for (final Move move : board.currentPlayer().getLegalMoves()) {
final MoveTransition moveTransition = board.currentPlayer().makeMove(move);
if (moveTransition.getMoveStatus().isDone()) {
final int currentValue =
board.currentPlayer().getColor().isWhite()
? min(moveTransition.getTransitionBoard(), depth - 1)
: max(moveTransition.getTransitionBoard(), depth - 1);
moveOrderEntries.add(new MoveOrderEntry(move, currentValue));
}
}
if (SORT_DESCENDING) {
Collections.sort(
moveOrderEntries,
new Comparator<MoveOrderEntry>() {
@Override
public int compare(final MoveOrderEntry o1, final MoveOrderEntry o2) {
return Ints.compare(o2.getScore(), o1.getScore());
}
});
} else {
Collections.sort(
moveOrderEntries,
new Comparator<MoveOrderEntry>() {
@Override
public int compare(final MoveOrderEntry o1, MoveOrderEntry o2) {
return Ints.compare(o1.getScore(), o2.getScore());
}
});
}
final List<Move> orderedMoves = new ArrayList<>();
for (final MoveOrderEntry entry : moveOrderEntries) {
orderedMoves.add(entry.getMove());
}
return ImmutableList.copyOf(orderedMoves);
}
private static boolean isEndGameScenario(final Board board) {
return board.currentPlayer().isInCheckMate()
|| board.currentPlayer().isInStaleMate()
|| board.currentPlayer().getOpponent().isInCheckMate()
|| board.currentPlayer().getOpponent().isInStaleMate();
}