com.barrybecker4.game.twoplayer.go.board.analysis.StringShapeAnalyzer Maven / Gradle / Ivy

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bb4-games java code.
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/** Copyright by Barry G. Becker, 2000-2011. Licensed under MIT License: http://www.opensource.org/licenses/MIT  */
package com.barrybecker4.game.twoplayer.go.board.analysis;

import com.barrybecker4.game.common.board.BoardPosition;
import com.barrybecker4.game.twoplayer.go.board.GoBoard;
import com.barrybecker4.game.twoplayer.go.board.elements.position.GoBoardPosition;
import com.barrybecker4.game.twoplayer.go.board.elements.position.GoStone;

/**
 * Checks the shape of the string just formed on the board
 * to determine if it is good or bad shape.
 *
 * @author Barry Becker
 */
public class StringShapeAnalyzer {

    private static final int EMPTY_TRIANGLE_PENALTY = 1;
    private static final int CLUMP_OF_FOUR_PENALTY = 1;

    private GoBoard board_;

    public StringShapeAnalyzer(GoBoard board) {
        board_ = board;
    }

    /**
     * @return a measure of the severity - a number corresponding to the number of clumps
     *  of 4 or empty triangles that this stone is connected to.
     * returns 0 if does not form bad shape at all. Large numbers indicate worse shape.
     * Possible bad shapes are :
     *  SHAPE_EMPTY_TRIANGLE :
     *   X -
     *   X X
     * SHAPE_CLUMP_OF_4 :
     *   X X
     *   X X
     */
    public int formsBadShape(GoBoardPosition position)
    {
        GoStone stone = (GoStone)position.getPiece();
        int r = position.getRow();
        int c = position.getCol();

        return checkBadShape(stone, r, c,  1,-1)
             + checkBadShape(stone, r, c, -1,-1)
             + checkBadShape(stone, r, c,  1, 1)
             + checkBadShape(stone, r, c, -1, 1);
    }

    /**
     *  There are 3 empty triangle cases based on where the stone is:
     *       adj1    diag   X       XX     X
     *       space adj2    XX     X      XX
     *
     * @param stone that forms part of the empty triangle
     * @return the amount to penalize for bad shape.
     */
    private int checkBadShape(GoStone stone, int r, int c, int incr, int incc) {
        boolean player1 = stone.isOwnedByPlayer1();

        if ( !board_.inBounds( r + incr, c + incc ) ) {
            return 0;
        }
        BoardPosition adjacent1 = board_.getPosition( r + incr, c );
        BoardPosition adjacent2 = board_.getPosition( r , c + incc);
        BoardPosition diagonal = board_.getPosition( r + incr, c + incc);

        int severityScore = 0;

        if (adjacent1.isOccupied() && adjacent2.isOccupied())  {
            if (   adjacent1.getPiece().isOwnedByPlayer1() == player1
                && adjacent2.getPiece().isOwnedByPlayer1() == player1)
                severityScore += getBadShapeAux(diagonal, player1);
        }

        if (adjacent1.isOccupied() && diagonal.isOccupied())  {
            if (   adjacent1.getPiece().isOwnedByPlayer1() == player1
                && diagonal.getPiece().isOwnedByPlayer1() == player1)
                severityScore += getBadShapeAux(adjacent2, player1);
        }

        if (adjacent2.isOccupied() && diagonal.isOccupied())  {
            if (   adjacent2.getPiece().isOwnedByPlayer1() == player1
                && diagonal.getPiece().isOwnedByPlayer1() == player1)
                severityScore += getBadShapeAux(adjacent1, player1);
        }
        return severityScore;
    }


    private static int getBadShapeAux( BoardPosition nearbySpace, boolean player1 ) {
        if (nearbySpace.isUnoccupied()) {
            return EMPTY_TRIANGLE_PENALTY;
        }
        if (nearbySpace.getPiece().isOwnedByPlayer1() == player1 )  {
            return CLUMP_OF_FOUR_PENALTY;
        }
        return 0;
    }
}