Count Primes

Description:

Count the number of prime numbers less than a non-negative number, n

class Solution {
public:
    int countPrimes(int n) {
        if (n < 2)
        {
            return 0;
        }
        bool prime[n];
        memset(prime, true, n*sizeof(bool));
        prime[0] = false;
        prime[1] = false;
    
        int result = 0;
        int limit = sqrt(n);

        for (int i = 2; i <= limit; i++)
        {
            if (prime[i])
            {
                for (int j = i*i; j < n; j += i)
                {
                    prime[j] = false;
                }
            }
        }

        for (int i = 0; i < n; i++)
        {
            if (prime[i])
            {
                result++;
            }
        }

        return result;
    }
};