素筛模板

 1 #include<iostream>
 2 #include<cstring>
 3
 4 #define MAX_N 10000000
 5
 6 using namespace std;
 7
 8 bool flag[MAX_N];
 9 int prime[MAX_N];
10
11 void solve()
12 {
13     memset(flag,1,sizeof(flag));
14     flag[1] = 0;
15     int con=0;
16     for(int i = 2; i < MAX_N; i++)
17     {
18         if(flag[i])
19         {
20             prime[con++] = i;
21             for(int j = 2*i; j < MAX_N; j+=i)
22                 flag[j] = 0;
23         }
24     }
25 }
26 int main()
27 {
28     solve();
29     return 0;
30 }