Prime Number of Set Bits in Binary Representation

算一下bit为1的个数, 然后看下个数是不是prime.

class Solution {
    public int countPrimeSetBits(int L, int R) {
        int count = 0;
        for(int i = L; i <= R; i++) {
            if(isPrime(countBit(i)))
                count++;
        }
        return count;
    }
    
    private int countBit(int n) {
        int res = 0;
        for(int i = 0 ; i < 32; i++) {
            if((n & (1 << i)) != 0)
                res++;
        }
        return res;
    }

     public boolean isPrime(int number) {
        if(number < 2)
            return false;
        int sqrt = (int) Math.sqrt(number) + 1;
        for (int i = 2; i < sqrt; i++) {
            if (number % i == 0) {
                return false;
            }
        }
        return true;
    }
}