九宫格算法

public class Demo4 {

    public static void main(String[] args) {

        int n = 5;

        // 0:向右,1:向下,2:向左,3：向上
        int direction = 0;

        // 行，列
        int row = 0, col = 0;

        int num = 0;

        int[] array = new int[n * n];
        while (array[row * n + col] == 0) {
            num++;
            array[row * n + col] = num;
            switch (direction) {
            case 0:
                col++;
                break;
            case 1:
                row++;
                break;
            case 2:
                col--;
                break;
            case 3:
                row--;
                break;
            }
            if (row == n || col == n || row == -1 || col == -1
                    || array[row * n + col] != 0) {
                direction++;
                if (direction == 4)
                    direction = 0;
                switch (direction) {
                case 0:
                    row++;
                    col++;
                    break;
                case 1:
                    row++;
                    col--;
                    break;
                case 2:
                    row--;
                    col--;
                    break;
                case 3:
                    row--;
                    col++;
                    break;
                }
            }
        }

        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                System.out.printf("%-3s", array[i * n + j]);
            }
            System.out.println();
        }
    }
}