Prime Arrangements | Leetcode #1175

class Solution {
    long long permutation(int count,int MOD){
        long long ans = 1;
        for(int i=2;i<=count;++i)
            ans = (ans*i)%MOD;
        return ans;
    }
public:
    int numPrimeArrangements(int n) {
        int MOD = 1e9+7;
        int count = 0;
        for(int i=2;i<=n;++i){
            bool isPrime = true;
            for(int j=2;j<=sqrt(i);++j){
                if(i%j==0){
                    isPrime = false;
                    break;
                }
            }
            if(isPrime==true)
                count++;
        }
        return (permutation(count,MOD)*permutation(n-count,MOD))%MOD;
    }
};