Android Open Source - minecraft-connect-4 Hard Ai

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License

The source code is released under:

MIT License

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Java Source Code

/* COPYRIGHT (C) 2014 Aleksandr Belkin. All Rights Reserved. */
package sq.squ1rr.mcc4.ai;
/*  w w w  .  j  a va  2  s  . c  o  m*/
import sq.squ1rr.mcc4.rules.Player;

/**
 * Hard AI. Anticipates a move from above, doesn't miss the gaps, starts in
 * the centre. Pretty much unbeatable unless you do two combinations of 3 with
 * a single gap in between.
 * @author Aleksandr Belkin
 */
public class HardAi extends EasyAi {
    /**
     * Create and initialise AI
     * @param grid
     */
    public HardAi(int[][] grid) {
        super(grid);
    }

    /*
     * (non-Javadoc)
     * @see sq.squ1rr.mcc4.ai.EasyAi#run()
     */
    @Override
    public int run() {
        int col = cols / 2; // start in the centre
        int alpha = 0;
        
        for(int i = 0; i < grid.length; ++i) {
            if(grid[i][0] != 0) continue;
            int j = findRow(i);
            int beta = analyse(i, j);
            if(beta > alpha) {
                alpha = beta;
                col = i;
            }
        }

        // lets be sure the move is valid
        return grid[col][0] == 0 ? col : super.run();
    }
    
    private int analyse(int x, int y) {
        int m = count(x, y, -1);
        
        if(y > 0 && m > count(x, y - 1, Player.PLAYER1)) return m;
        
        return y == 0 ? m : 0;
    }
    
    private int count(int x, int y, int p) {
        int com = 0;
        com = Math.max(com, countCom(x, y, X_L, 0,      p));
        com = Math.max(com, countCom(x, y, X_L, Y_T,    p));
        com = Math.max(com, countCom(x, y, X_L, Y_B,    p));
        com = Math.max(com, countCom(x, y, 0,   Y_T,    p));
        return com;
    }
    
    private int countCom(int x, int y, int i, int j, int p) {
        int com = 0;
        
        int i2 = -i;
        int j2 = -j;
        
        if(p == -1) {
            // count both player combinations possible (from both sides)
            int temp = 0;
            temp += combination(x + i, y + j, i, j, Player.PLAYER1);
            temp += combination(x + i2, y + j2, i2, j2, Player.PLAYER1);
            com = Math.max(temp, com);
            temp += combination(x + i, y + j, i, j, Player.PLAYER2);
            temp += combination(x + i2, y + j2, i2, j2, Player.PLAYER2);
            com = Math.max(temp, com);
        } else { // count one player combinations (from both sides)
            int temp = 0;
            temp += combination(x + i, y + j, i, j, p);
            temp += combination(x + i2, y + j2, i2, j2, p);
            com = Math.max(temp, com);
        }
        
        return com;
    }
}

Java Source Code List