在埃拉托斯特尼筛法中 ，要筛选出不⼤于n的所有素数 ，最外层循环应该遍历什么范围 ( ) ?
1 vector<int> sieveOf Eratosthenes(int n) {
2 std::vector<bool> isPrime(n + 1, true);
3 std::vector<int> primes;
4 {
5 if (isPrime[i]) {
6 primes.push_back(i);
7 for (int j = i * i; j <= n; j += i) {
8 isPrime[j] = false;
9 }
10 }
11 }
12 for (int i = sqrt(n) + 1; i <= n; ++i) {
13 if (isPrime[i]) {
14 primes.push_back(i);
15 }
16 }
17 return primes;
18 }
for (int i = 2; i <= n; ++i)
for (int i = 1; i < n; ++i)
for (int i = 2; i <= sqrt(n); ++i)
for (int i = 1; i <= sqrt(n); ++i)