C++
int primes[N], cnt; // primes[]存储所有素数
bool st[N]; // st[x]存储x是否被筛掉
void get_primes(int n)
{
for (int i = 2; i <= n; i ++ )
{
if (!st[i]) primes[cnt ++ ] = i;
for (int j = 0; primes[j] <= n / i; j ++ )
{
st[primes[j] * i] = true;
if (i % primes[j] == 0) break;
}
}
}
Python
def check(num) :
flag = [True] * (num + 1)
prime = []
for i in range(2,num+1) :
if flag[i] :
prime.append(i)
j = 0
while prime[j] <= num // i :
flag[prime[j] * i] = False
if i % prime[j] == 0 : break
j += 1
return prime