#include <iostream>  
using namespace std;

int judge(int);

int main()
{
	cout << "验证哥德巴赫猜想：一个不小于6的偶数可以表示为两个素数之和" << endl << endl;

	int border, num, front;
	
	cout << "请输入欲验证的最大值：";
	cin >> border;

	for (num = 6; num <= border; num = num + 2)
	{
		for (front = 3; front <= num / 2; front = front + 2)
		{
			//先把num表示为front和另一个奇数behind之和，再判断这两个奇数是否为素数
			int behind = num - front;

			if ((judge(front) == 1) & (judge(behind) == 1))
			{
				cout << num << "=" << front << "+" << behind << endl;
			}
		}
	}

	system("pause");
	return 0;
}

int judge(int tmp)
{
	for (int i = 3; i <= sqrt(tmp); i = i + 2)
	{
		if (tmp % i == 0) return 0;	//只要能被一个奇数整除，它就不是素数
	}

	//要遍历所有奇数才能说它是素数
	return 1;
}