求前n个素数（C++）

 1 #include<iostream>
 2 #include <math.h>
 3 using namespace std;
 4 
 5 class Sushu
 6 {
 7 public:
 8 
 9     Sushu()
10     {
11         num = 2;
12     }
13 
14     ~Sushu()
15     {
16     }
17 
18     bool isSushu()
19     {
20         for (int i = 2; i <=sqrt(num); i++)
21         {
22             if (num%i == 0)
23                 return false;
24         }
25         return true;
26     }
27 
28     int getSushu()
29     {
30         return num;
31     }
32 
33     void printN_Sushu(int n)
34     {
35         int counter=0;
36         cout << endl;
37         while (counter<n)
38         {        
39             if (isSushu())
40             {
41                 counter++;
42                 cout<<"第"<<counter<<"个素数是："<<getSushu()<<endl;                
43                 num++;
44             }
45             else
46             {
47                 num++;
48             }
49         }
50 
51     }
52 
53 private:
54     int num;
55 };
56 
57 int main()
58 {
59     int n;
60     cout << "n的值为：";
61     cin >> n;
62 
63     Sushu sushu;
64     sushu.printN_Sushu(n);
65 
66     return 0;
67 }