Delete_The _Selected_Prime

 1 #include <iostream>
 2 #include <cmath>
 3 #define N 99999
 4 
 5 using namespace std;
 6 
 7 bool flag[N];
 8 
 9 void prime()
10 {
11     for (int i = 2; i < N; i++)
12     {
13         if (i % 2 == 0)
14         {
15             flag[i] = false;
16         }
17         else
18         {
19             flag[i] = true;
20         }
21     }
22     for (int i = 3; i < sqrt(N); i+= 2)
23     {
24         if (flag[i])
25         {
26             for (int j = i + i; j < N; j+= i)
27             {
28                 flag[j] = false;
29             }
30         }
31     }
32 
33     for (int i = 2; i < 100; i++)
34     {
35         if (flag[i])
36         {
37             cout << i << endl;
38         }
39     }
40 }
41 
42 int main()
43 {
44     prime();
45     return 0;
46 }