腾讯面试编程给定一个正整数，编写程序计算有多少对质数的和等于输入的这个正整数，并输出结果。

输入描述:

输入包括一个整数n,(3 ≤ n < 1000)

输出描述:

输出对数

输入例子1:

10

输出例子1:

2

import java.util.Scanner;

public class Test7 {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int count  = 0;
        for(int i=2;i<=n/2;i++){
            if(IsPrime(i) && IsPrime(n-i))
                count++;
        }
        System.out.println(count);
    }
    
    public static boolean IsPrime(int num) {
        if (num <= 1)
            return false;
        if (num == 2)
            return true;

        boolean flag = false;
        for (int i = 2; i <= Math.sqrt(num); i++) {
            if(num % i == 0){
                flag = true;
                break;
            }
        }
        if(flag){
            return false;
        }else{
            return true;
        }
    }
}

#include<iostream>  
using namespace std;  
int is_prime_number(int);  
int main(int argc, char const *argv[])  
{  
    int num;  
    int num_first[1000];  
    int num_second[1000];  
    int count = 0;  
    int flag = 0;  
    while (cin >> num)  
    {  
        for (int i = 2; i < num; ++i)  
        {  
            for (int j = 2; j < num; ++j)  
            {  
                if (num == i + j)  
                {  
                    if (is_prime_number(i) && is_prime_number(j))  
                    {  
                        num_first[count] = i;  
                        num_second[count] = j;  
                        count++;  
                        flag = 1;  
                    }  
                }  
            }  
        }  
        if (flag == 1)  
        {  
            cout << (count + 1) / 2 << endl;  
        }  
        for (int i = 0; i < count; ++i)  
        {  
            printf("(%d,%d)\n", num_first[i], num_second[i]);//输出质数组  
        }  
    }  
    return 0;  
}  
int is_prime_number(int num)  
{  
    int n;  
    for (n = 2; n <= num / 2; n++)  
    {  
        if (num % n == 0){  
            return 0;  
        }  
    }  
    return 1;  
}