Java Connect 4 Algorithm Checking for a win

Question

I am trying to check for a win in a connect 4 game, I managed to check diagonall right, But I need help with checking diagonally left, vertically and horizontally, Its a matter of changing the algorithm I have already created and tweaking it. How do you check vertically, horizontally and diagonally left?

public class Game {

    private static final int COLS = 7;
    private static final int ROWS = 6;
    public State[][] count = new State[COLS][ROWS];
    boolean player1Turn = true;
    public static final int LEN = 4;
    protected Context context;

    public enum State {
        RED, YELLOW, BLANK;
    }

    public State checkWinner() {
        for (int col = 0; col < count.length; ++col) {
            for (int row = 0; row < count[col].length; ++row) {
                State result = checkWinner(col, row);
                if (result != null) {
                    return result;
                }
            }
        }
        return null;
    }

    //This method is called in a another class 
    public State checkWinner(int col, int row) {
        State cell = count[col][row];
        if (cell == null || cell == State.BLANK) {
            return null;
        }

        // Here I am checking for a win Diagonally  Right
        // The next step is to check vertically and horizontelly and Diagnollly left
        // There needs to be a pattern of four reds or yellow counters either horizontelly or vertically 
        // My guess to check horizentally or vertically and diagonally left would be to copy this algorithm and possibly change the coordinates 
        // Checking four up for horizontal and four across for vertical, four for diagnoally left
        if ((col + LEN <= COLS) && (row + LEN <= ROWS)) {
            boolean same = true;
            for (int i = 1; i < LEN; ++i) {
                if (count[col + i][row + i] != cell) {
                    same = false;
                    break;
                }
            }
            if (same) {
                return cell;
            }
        }
        // TODO Auto-generated method stub
        return null;
    }
}

start at the end of the rows and work your way to the beginning. — pedromss, Feb 11 '14 at 12:52
If you just want something working check http://stackoverflow.com/questions/7033165/algorithm-to-check-a-connect-four-field . (I've not tested it though) — StephaneM, Feb 11 '14 at 12:59
Question rolled back. Please do not delete your code as it invalidates your question. -1. — Hovercraft Full Of Eels, Feb 11 '14 at 15:48
Again -- please stop deleting your code. Question again rolled back to show code. Moderators flagged for action on this question. — Hovercraft Full Of Eels, Feb 11 '14 at 17:47
We can keep on doing this rollback war for as long as you wish. Also note that I will post your code on another site that I'm hosting just in case your reason for deleting it is to hide this question and your code from your instructors. — Hovercraft Full Of Eels, Feb 11 '14 at 20:24

score 1 · Answer 1 · answered Feb 11 '14 at 12:56

1

Say it is a 4x4 square, to check for diagonally right, you are comparing the cell state starting from (top left) position (0,0) till the bottom right cell (4,4).

To check diagonally left, do the reverse, i.e., start from the top right corner and end with bottom left corner - (0,4) to (4,0)

To check vertically, traverse through each column (0,0) till (4,0) - do this for every column you want to check.

Same applies for horizontal check, traverse through left most cell to right most cell in each row - (0,0) till (0,4), (1,0) to (1,4) and so on..

Hope it helps!

answered Feb 11 '14 at 12:56

Rakesh

4,264
4
32
58

Reversing diagonally left? Can I not just use the algorithm I already have for that? What do I change in that? – user3297206 Feb 11 '14 at 12:58
Yes, you can use the algorithm you already have for diagonally left. I forgot about it while writing the answer! – Rakesh Feb 12 '14 at 13:21
Why are you using a 4x4 square? the board itself is 6x7. – Ungeheuer Jun 11 '15 at 05:16

score 0 · Answer 2 · answered Feb 11 '14 at 13:01

0

It's quite simple.

You have your point : (col,row).

Check horizontal: check every cell in the same row one by one from left to right, and count if you have more than 4 consecutive filled cell. If yes player win with horizontal method.

Same for vertical: check every cell in the same col one by one fromt top to bottom, and count if you have more than 4 consecutive filled cell. If yes player win with vertical method.

answered Feb 11 '14 at 13:01

beny1700

284
1
4
10

I cant figure out the algorithm – user3297206 Feb 11 '14 at 13:02

Java Connect 4 Algorithm Checking for a win

2 Answers2