蓝桥杯 方格分割 JAVA

public class Main {
    static int res = 0;
    static boolean [][] rec = new boolean[7][7];
    static int[][] dir = {
             {0, 1},
             {0, -1},
             {1, 0},
             {-1, 0}
    };

    public static void main(String[] args) {
        rec[3][3] = true;
        f(3, 3);
        System.out.println(res/4);
    }
    public static void f(int x,int y){
        if (x == 0 || x == 6 || y == 0 || y == 6) {
            res++;
            return;
        }
        for (int i = 0; i < 4; i++) {
            int dx = x + dir[i][0];
            int dy = y + dir[i][1];
            if (rec[dx][dy] == false){
                rec[dx][dy] = true;
                rec[6-dx][6-dy] = true;
                f(dx, dy);
                rec[6-dx][6-dy] = false;
                rec[dx][dy] = false;
            }
        }
    }
}