- Changed the rules. Now tiles can only be placed next to existing tiles. Unless the board is empty.

src/model/Board.java

@@ -12,6 +12,66 @@ public class Board {
 	public static final int NUM_ROWS = 5;
 	public static final int ROW_REMOVAL_SIZE = 3;
 
+	public static boolean isLegal(Board brd, CellPointer cp) {
+		if (cp.r < 0 || cp.r >= Board.NUM_ROWS || cp.c < 0
+				|| cp.c >= Board.NUM_COLS) {
+			return false;
+		}
+
+		boolean legal = (brd.getTile(cp.r, cp.c) == TileColor.NONE);
+
+		boolean rowUp = (cp.r - 1) >= 0;
+		boolean rowDown = (cp.r + 1) < Board.NUM_ROWS;
+		boolean colUp = (cp.c - 1) >= 0;
+		boolean colDown = (cp.c + 1) < Board.NUM_COLS;
+
+		// r-1 / c-1
+		if (rowUp && colUp
+				&& (brd.getTile(cp.r - 1, cp.c - 1) != TileColor.NONE)) {
+			return legal && true;
+		}
+
+		// r-1 / c
+		if (rowUp && (brd.getTile(cp.r - 1, cp.c) != TileColor.NONE)) {
+			return legal && true;
+		}
+
+		// r-1 / c+1
+		if (rowUp && colDown
+				&& (brd.getTile(cp.r - 1, cp.c + 1) != TileColor.NONE)) {
+			return legal && true;
+		}
+
+		// r / c-1
+		if (colUp && (brd.getTile(cp.r, cp.c - 1) != TileColor.NONE)) {
+			return legal && true;
+		}
+
+		// r / c+1
+		if (colDown && (brd.getTile(cp.r, cp.c + 1) != TileColor.NONE)) {
+			return legal && true;
+		}
+
+		// r+1 / c-1
+		if (rowDown && colUp
+				&& (brd.getTile(cp.r + 1, cp.c - 1) != TileColor.NONE)) {
+			return legal && true;
+		}
+
+		// r+1 / c
+		if (rowDown && (brd.getTile(cp.r + 1, cp.c) != TileColor.NONE)) {
+			return legal && true;
+		}
+
+		// r+1 / c+1
+		if (rowDown && colDown
+				&& (brd.getTile(cp.r + 1, cp.c + 1) != TileColor.NONE)) {
+			return legal && true;
+		}
+
+		return brd.isEmpty();
+	}
+
 	private final TileColor[][] board;
 
 	// a Ply is a play by 1 side. Increments each time setTile() is called.
@@ -62,7 +122,7 @@ public class Board {
 	}
 
 	public int getTurn() {
-		return (numPlies + 1)/ 2;
+		return (numPlies + 1) / 2;
 	}
 
 	@Override
@@ -90,8 +150,8 @@ public class Board {
 	}
 
 	public boolean playTile(CellPointer cp, TileColor tile) {
-		if (board[cp.r][cp.c] != TileColor.NONE) {
+		if (!isLegal(this, cp)) {
-			return false; // illegal move
+			return false; // Illegal move.
 		}
 
 		board[cp.r][cp.c] = tile;
@@ -247,4 +307,16 @@ public class Board {
 		}
 		return sb1.toString();
 	}
+
+	private boolean isEmpty() {
+		for (int r = 0; r < Board.NUM_ROWS; r++) {
+			for (int c = 0; c < Board.NUM_COLS; c++) {
+				if (getTile(r, c) != TileColor.NONE) {
+					return false;
+				}
+			}
+		}
+
+		return true;
+	}
 }

src/model/comPlayer/generator/AlphaBetaMoveGenerator.java

@@ -11,9 +11,9 @@ import model.SearchResult;
 import org.apache.log4j.Logger;
 
 public class AlphaBetaMoveGenerator implements MoveGenerator {
+	private static final int DEFAULT_RECURSIVE_PLAYS = 1;
 	private static final Logger LOGGER = Logger
 			.getLogger(AlphaBetaMoveGenerator.class.getName());
-	private static final int DEFAULT_RECURSIVE_PLAYS = 2;
 
 	private final BoardScorer scorer = new BoardScorer();
 	private final ValidMoveGenerator validMoveGenerator = new ValidMoveGenerator();
@@ -22,24 +22,34 @@ public class AlphaBetaMoveGenerator implements MoveGenerator {
 	public Move genMove(Board board, boolean asHuman) {
 
 		if (!asHuman) {
-			return getMaxValue(board, asHuman, DEFAULT_RECURSIVE_PLAYS * 2, Integer.MIN_VALUE,
+			return getMaxValue(board, asHuman, DEFAULT_RECURSIVE_PLAYS * 2,
-					Integer.MAX_VALUE).move;
+					Integer.MIN_VALUE, Integer.MAX_VALUE).move;
 		} else {
-			return getMinValue(board, asHuman, DEFAULT_RECURSIVE_PLAYS * 2, Integer.MIN_VALUE,
+			return getMinValue(board, asHuman, DEFAULT_RECURSIVE_PLAYS * 2,
-					Integer.MAX_VALUE).move;
+					Integer.MIN_VALUE, Integer.MAX_VALUE).move;
 		}
 	}
 
-	private SearchResult  getMaxValue(Board board, boolean asHuman, int recursionLevel,
+	/**
-			int alpha, int beta) {
+	 * AlphaBetaMoveGenerator2 does not support this method.
+	 */
+	@Override
+	public List<Move> genMoves(Board board, boolean asHuman, int nMoves) {
+		Move[] doNothing = new Move[] { Move.NONE };
+		LOGGER.info("Minimax genMoves() stub returning []");
+		return Arrays.asList(doNothing);
+	}
+
+	private SearchResult getMaxValue(Board board, boolean asHuman,
+			int recursionLevel, int alpha, int beta) {
 		if (recursionLevel < 1) {
-			return new SearchResult(Move.NONE,scorer.getScore(board));
+			return new SearchResult(Move.NONE, scorer.getScore(board));
 		}
 
 		List<Move> validMoves = validMoveGenerator.genMoves(board, asHuman,
 				MoveGenerator.ALL_MOVES);
 
-		SearchResult bestResult = new SearchResult(Move.NONE,Integer.MIN_VALUE);
+		SearchResult bestResult = new SearchResult(Move.NONE, Integer.MIN_VALUE);
 
 		if (validMoves.size() == 0) {
 			return bestResult;
@@ -53,8 +63,8 @@ public class AlphaBetaMoveGenerator implements MoveGenerator {
 						"Illegal move attempted during search!");
 			}
 
-			SearchResult searchResult = new SearchResult(nextMove,getMinValue(nextBoard, !asHuman, recursionLevel - 1,
+			SearchResult searchResult = new SearchResult(nextMove, getMinValue(
-					alpha, beta).score);
+					nextBoard, !asHuman, recursionLevel - 1, alpha, beta).score);
 
 			if (searchResult.compareTo(bestResult) > 0) {
 				bestResult = searchResult;
@@ -70,16 +80,16 @@ public class AlphaBetaMoveGenerator implements MoveGenerator {
 		return bestResult;
 	}
 
-	private SearchResult getMinValue(Board board, boolean asHuman, int recursionLevel,
+	private SearchResult getMinValue(Board board, boolean asHuman,
-			int alpha, int beta) {
+			int recursionLevel, int alpha, int beta) {
 		if (recursionLevel < 1) {
-			return new SearchResult(Move.NONE,scorer.getScore(board));
+			return new SearchResult(Move.NONE, scorer.getScore(board));
 		}
 
 		List<Move> validMoves = validMoveGenerator.genMoves(board, asHuman,
 				MoveGenerator.ALL_MOVES);
 
-		SearchResult bestResult = new SearchResult(Move.NONE,Integer.MAX_VALUE);
+		SearchResult bestResult = new SearchResult(Move.NONE, Integer.MAX_VALUE);
 
 		if (validMoves.size() == 0) {
 			return bestResult;
@@ -93,8 +103,8 @@ public class AlphaBetaMoveGenerator implements MoveGenerator {
 						"Illegal move attempted during search!");
 			}
 
-			SearchResult searchResult = new SearchResult(nextMove,getMaxValue(nextBoard, !asHuman, recursionLevel - 1,
+			SearchResult searchResult = new SearchResult(nextMove, getMaxValue(
-					alpha, beta).score);
+					nextBoard, !asHuman, recursionLevel - 1, alpha, beta).score);
 
 			if (searchResult.compareTo(bestResult) < 0) {
 				bestResult = searchResult;
@@ -109,14 +119,4 @@ public class AlphaBetaMoveGenerator implements MoveGenerator {
 
 		return bestResult;
 	}
-
-	/**
-	 * AlphaBetaMoveGenerator2 does not support this method.
-	 */
-	@Override
-	public List<Move> genMoves(Board board, boolean asHuman, int nMoves) {
-		Move[] doNothing = new Move[] { Move.NONE };
-		LOGGER.info("Minimax genMoves() stub returning []");
-		return Arrays.asList(doNothing);
-	}
 }

src/model/comPlayer/generator/ValidMoveGenerator.java

@@ -6,6 +6,7 @@ import java.util.List;
 
 import model.Board;
 import model.Board.TileColor;
+import model.CellPointer;
 import model.Move;
 
 import org.apache.log4j.Logger;
@@ -25,14 +26,14 @@ public class ValidMoveGenerator implements MoveGenerator {
 
 		List<Move> validMoves = new ArrayList<Move>();
 
-		for (int i = 0; i < Board.NUM_ROWS; i++) {
+		for (int r = 0; r < Board.NUM_ROWS; r++) {
-			for (int j = 0; j < Board.NUM_COLS; j++) {
+			for (int c = 0; c < Board.NUM_COLS; c++) {
-				if (board.getTile(i, j) == TileColor.NONE) {
+				if (Board.isLegal(board, new CellPointer(r, c))) {
 					for (TileColor color : TileColor.values()) {
 						if (color == TileColor.NONE) {
 							continue;
 						}
-						validMoves.add(new Move(color, i, j));
+						validMoves.add(new Move(color, r, c));
 					}
 				}
 			}
@@ -43,7 +44,7 @@ public class ValidMoveGenerator implements MoveGenerator {
 		if (nMoves == MoveGenerator.ALL_MOVES) {
 			return validMoves;
 		} else {
-			return validMoves.subList(0, Math.min(validMoves.size(),nMoves));
+			return validMoves.subList(0, Math.min(validMoves.size(), nMoves));
 		}
 	}
 }