2022.4.5-----leetcode.762

 //比较奇怪的质数判断法
boolean isPrime(int num){
        if (num == 1)
            return false;
        if (num == 2 || num == 3)
            return true;
        if (num % 6 != 1 && num % 6 != 5)
            return false;
        int end = (int) Math.pow(num,1.0/2 );
        for (int i = 5; i <= end; i += 6) {
            if (num % i == 0 || num % (i + 2) == 0)
                return false;
        }
        return true;
    }
 public int countPrimeSetBits(int l, int r) {
        int ans=0;
        for (int i = l; i <=r ; i++) {
            int num=Integer.bitCount(i);
            if(isPrime(num))
                ans++;
        }
        return ans;
    }