第七届蓝桥B组java省赛剪邮票

public class test {
    public static int count, t;
    public static int[][] book = new int[6][6];
    public static int[] num = new int[5];
    public static int[] x = new int[] { 1, 0, -1, 0 };
    public static int[] y = new int[] { 0, 1, 0, -1 };

    public static void dfs1(int sx, int sy) {
        for (int i = 0; i < 4; ++i) {
            int ex = sx + x[i];
            int ey = sy + y[i];
            if (ex < 1 || ex > 3 || ey < 1 || ey > 4)
                continue;
            if (book[ex][ey] == 1) {
                ++t;
                book[ex][ey] = 0;
                dfs1(ex, ey);
            }
        }
    }

    public static void dfs(int i, int j) {
        if (i == 5) {
            for (int ii = 0; ii < 6; ++ii) {
                for (int jj = 0; jj < 6; ++jj) {
                    book[ii][jj] = 0; // 避免上一步的残留
                }
            }
            int sx = 0, sy = 0;
            for (int k = 0; k < 5; ++k) {
                sy = num[k] % 4;
                if (sy == 0) {
                    sy = 4;
                    sx = num[k] / 4;
                } else {
                    sx = num[k] / 4 + 1;
                }
                book[sx][sy] = 1;
            }
            t = 1;
            book[sx][sy] = 0; // 从最后一个点查找,算第一步了
            dfs1(sx, sy); // 5个点是否连通，走迷宫
            if (t == 5) {
               ++count;
               t = 0;
            }
        } else {
            for (; j < 13; ++j) {
                num[i] = j;
                dfs(i + 1, j + 1);
            }
        }
    }

    public static void main(String[] args) {
        dfs(0, 1);
        System.out.println(count);
    }
}