leetcode

0 class Solution {

1 public:

2 int countPrimes(int n) {

3 vector<bool> sieve(n);

4 int res = 0;

5 for (long i = 2; i < n; i++) {

6 if (sieve[i]) continue;

7 for (long j = i * i; j < n; j += i)

8 sieve[j] = true;

9 res++;

10 }

11 return res;

12 }

13 };