[Level 1][C++] 소수 찾기

#include <string>
#include <vector>
#include <cmath>

using namespace std;

int solution(int n) {
       bool *arr = new bool[n + 1];
           int answer = 0;

       for (int i = 0; i < n + 1; i++)
              arr[i] = true;

       for (int i = 2; i <= sqrt(n); i++)
       {
              if (!arr[i])
              continue;
              for (int j = i * i; j <= n; j += i)
                     arr[j] = false;
       }

       for (int i = 2; i < n + 1; i++)
              if (arr[i])
                     answer++;
    
           return answer;
}