在二维数组中搜索对角线

Question

I am trying to search diagonally in a 2D array for a connect four game. I thought I had it figured out, but apparently I am wrong. The first set of for loops work fine, searching right to left, diagonally. The second set of for loops, do not work. I thought all i had to do was switch some positive signs to negative and it work. Eventually, I was able to get it to work partially, by changing the GRID_HEIGHT-1...BUT, I keep getting bound errors. Any help at this point would be greatly appreciated. Also, the grid for the 2d array is 5x4. So its really connect 3.

    for (int y = 0; y <= GRID_HEIGHT-3; y++) {
        for (int x = 0; x <= GRID_WIDTH-3; x++) {
            if (    
                    state[y][x] != Player.NONE && 
                    state[y][x] == state[y+1][x+1] &&
                    state[y+1][x+1] == state[y+2][x+2]
                    ) return state[y][x];
        }
    }
    for (int y = 0; y <= GRID_HEIGHT-3; y++) {
        for (int x = 0; x <= GRID_WIDTH-3; x++) {
            if (    
                    state[y][x] != Player.NONE && 
                    state[y][x] == state[y-1][x-1] &&
                    state[y-1][x-1] == state[y-1][x-2]
                    ) return state[y][x];
        }
    }


    return Player.NONE;

}

Answer 1

For the second set of loops, you are subtracting from the indexes, which means that the index can go below zero. You need the loop to start above zero.

for (int y = 2; y < GRID_HEIGHT; y++) {
    for (int x = 2; x < GRID_WIDTH; x++) {
        if (    
                state[y][x] != Player.NONE && 
                state[y][x] == state[y-1][x-1] &&
                state[y-1][x-1] == state[y-2][x-2]
                ) return state[y][x];
    }
}

Also, generally you should be saying (x < GRID_HEIGHT) rather than (x <= GRID_HEIGHT-1) when applicable as the second is harder to read.

Answer 2

从GRID_HEIGHT向下迭代到GRID_HEIGHT-3 ，而不是从0迭代到GRID_HEIGHT-3 3。