第七届蓝桥B组java省赛方格填数

public class test {
    public static int[] a = new int[12];
    public static int[] book = new int[12];
    public static int count = 0;

    public static void solve(int i) {
        if (i == 11) {
            ++count;
        } else {
            for (int j = 0; j < 10; ++j) {
                if (checked(i, j)) { // j是准备尝试的数字
                    book[j] = 1; // 标志0-9是否用过
                    a[i] = j; 
                    solve(i + 1);
                    a[i] = -2; // 为了和0-9不相邻，-1和0相邻，不行，设为任意不相邻数字即可
                    book[j] = 0;
                }
            }
        }
    }

    public static boolean checked(int i, int j) { // 暴力检索
        if (book[j] != 0)
            return false;
        switch (i) {
        case 1: // a[1]直接放
            break;
        case 2: // a[2]看a[1]情况
            if (j == a[1] + 1 || j == a[1] - 1)   return false;
            break;
        case 3: // a[3]看a[2]情况
            if (j == a[2] + 1 || j == a[2] - 1)   return false;
            break;
        case 4:
            if (j == a[1] + 1 || j == a[1] - 1)   return false;
            break;
        case 5: // a[5]看a[1]a[2]a[4]情况，下同
            if (j == a[1] + 1 || j == a[1] - 1)   return false;
            if (j == a[2] + 1 || j == a[2] - 1)   return false;
            if (j == a[4] + 1 || j == a[4] - 1)   return false;
            break;
        case 6:
            if (j == a[1] + 1 || j == a[1] - 1)   return false;
            if (j == a[2] + 1 || j == a[2] - 1)   return false;
            if (j == a[3] + 1 || j == a[3] - 1)   return false;
            if (j == a[5] + 1 || j == a[5] - 1)   return false;
            break;
        case 7:
            if (j == a[2] + 1 || j == a[2] - 1)   return false;
            if (j == a[3] + 1 || j == a[3] - 1)   return false;
            if (j == a[6] + 1 || j == a[6] - 1)   return false;
            break;
        case 8:
            if (j == a[4] + 1 || j == a[4] - 1)   return false;
            if (j == a[5] + 1 || j == a[5] - 1)   return false;
            break;
        case 9:
            if (j == a[4] + 1 || j == a[4] - 1)   return false;
            if (j == a[5] + 1 || j == a[5] - 1)   return false;
            if (j == a[6] + 1 || j == a[6] - 1)   return false;
            if (j == a[8] + 1 || j == a[8] - 1)   return false;
            break;
        case 10:
            if (j == a[5] + 1 || j == a[5] - 1)   return false;
            if (j == a[6] + 1 || j == a[6] - 1)   return false;
            if (j == a[7] + 1 || j == a[7] - 1)   return false;
            if (j == a[9] + 1 || j == a[9] - 1)   return false;
            break;
        }
        return true;
    }

    public static void main(String[] args) {
        for (int i = 0; i < 12; ++i) {
            a[i] = -2;
        }
        solve(1); // a[0]和a[11]不使用，从下标1开始
        System.out.println(count);
    }
}