1 #include<iostream>
 2 #include<string>
 3 #include<bitset>
 4 #include<cmath>
 5 
 6 using
 
 namespace std;
 7 int main()
 8 {
 9     int const max_number(32);
10     int const max_test((int)sqrt((double)max_number));
11     bitset<max_number + 1> number;
12     number.set();
13     number[1] = 0;
14     for (int i(1); i!=max_test; ++i)
15     {
16         if (number[i]){
17             //
 
篩掉倍數
18             for (int j(i*i); j <max_number + 1; j += i)
19             {
20                 number[j] = 0;
21             }
22         }
23     }
24     cout << "The number of the primes less than " << max_number + 1
25         << "is" << number.count() << endl;
 
26     for (int i(1); i != max_number + 1; ++i)
27     {
28         if (number[i]) cout << i << ",";
29     }
30     cout << endl;
31     system("pause");
32 }

埃拉托斯特尼--篩法 c++求質數，用bitset類型