只有两个测试点AC

#include <iostream>
#include <cmath>

using namespace std;

int fun(int X) //判断是否为质数
{
	int flag = 1;
	for (int i = 2; i <= sqrt(X); i++)
	{
		if (X % i == 0)
		{
			flag = 0;
			break;
		}
	}
	if (flag == 1)
		return 1;
}
int main()
{
	int N;
	cin >> N;
	for (int i = 4; i <= N; i+=2)
	{
		for (int j = 2; j <= sqrt(N); j++)
		{
			if (fun(j) && fun(i - j))
			{
				cout << i << "=" << j << "+" << i - j << endl;
				break;
			}
		}
	}
	system("pause");
	return 0;
}