筛选法求n以内所有的素数

 1 #include<iostream>
 2 
 3 using namespace std;
 4 
 5 int main()
 6 {
 7     int n,i,j;
 8 
 9     cin >> n;
10 
11     int *p = new int[n + 1];
12 
13     for (i = 0; i <= n; ++i)
14         p[i] = 1;
15 
16 
17     for (i = 2; i <= n; ++i)
18     {
19         if (p[i])
20         {
21             for (j = 2; i*j <= n; ++j)
22                 p[i*j] = 0;
23         }
24     }
25 
26     for (i = 2; i <= n; ++i)
27         if (p[i])
28             cout << i << " ";
29 
30     cout << endl;
31 
32     delete[] p;
33 
34     return 0;
35 }