[MM36-易] Prime Numbers(C++)

[MM36-易] Prime Numbers

Problem Description
An integer n is said to be a prime number if it is greater than 1 and has only factors of 1 and itself. For example, 2, 3, 5, and7 are prime numbers, but 4, 6, 8 and 9 are not. This problem asks you to calculate the number of prime numbers less than a given integer N.
Technical Specification
2 ≤ N ≤ 30000
Input File Format
The input data consists of several lines, each line contains one integer 2 ≤ N ≤ 30000. The end of input is indicated by a number 0. There are at most 6 test cases.
Output Format
For each case, print the number of primenumbers less than N.
Example

Sample Input:	Sample Output:
3 10 15 32 0	1 4 6 11

1. #include <iostream>  
2. #include <string>  
3. #include <sstream>  
4. #include <stdio.h>  
5. #include <ctype.h>  
6. #include <cmath>  
7. using namespace std;  
8.   
9. int main() {  
10.     // [MM36-易] Prime Numbers  
11.     string Num;  
12.     while(getline(cin, Num))  
13.     {  
14.         int num = stoi(Num);  
15.         int count = 0;  
16.         if(num != 0)  
17.         {  
18.             for(int i = 1;i < num;i++)  
19.             {  
20.                 int c = 0;  
21.                 for(int j = 1;j <= i;j++)  
22.                 {  
23.                     if(i % j == 0)  
24.                     {  
25.                         c++;  
26.                     }  
27.                 }  
28.                 if(c == 2 && num != 1)  
29.                 {  
30.                     count++;  
31.                 }  
32.             }  
33.             cout << count << endl;  
34.         }  
35.         else  
36.         {  
37.             break;  
38.         }  
39.     }  
40.     return 0;  
41. }