https://leetcode.cn/problems/special-permutations/description/?envType=daily-question&envId=2024-06-26

class Solution {
public:
    int mod =  1e9 + 7;   
    int n;
    int specialPerm(vector<int>& nums) {
        vector<vector<int>> dp(1 << 14,  vector<int>(15, 0));
        n = nums.size();
        for (int i = 0; i < n; i++) {
            dp[1 << i][i] = 1;
        }
        for (int i = 1; i < 1 << n; i ++) {
            for (int j = 0; j < n; j++) {
                if ((i >> j &1) == 0) continue;
                int t = i;
                for (int  k = 0; k < n; k++) {
                    if( k == j  || (i >> k & 1) == 0)  continue;
                    if ( (nums[k] % nums[j] == 0 || nums[j] % nums[k] == 0 )) {
                        dp[i][j] = (dp[i][j] +  dp[t - (1 << j)][k]) % mod;
                    }
                }
            }
        }
        long long res = 0;
        for (int i = 0; i < n; i++) res =  (res + dp[(1 << n) -1][i] )%  mod;
        return res;
    }
};