543 - GoldBach's Conjecture

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <fstream>
using namespace std;

int prime_list[1000001];

int main()
{
	ofstream out("output.txt");
	//memset(prime_list, 0, sizeof(prime_list));
	prime_list[0] = 1;
	prime_list[1] = 1;
	vector<int>v;
	v.push_back(2);
	v.push_back(3);
	v.push_back(5);
	v.push_back(7);
	v.push_back(11);
	v.push_back(13);
	v.push_back(17);
	v.push_back(19);
	v.push_back(23);

	for (int i = 0; i < v.size();i++)
	{
		int a = v[i];
		for (int j = 2; j <= 400; j++)
		{
			if (a != j && (j % a == 0))
			{
				prime_list[j] = 1;
			}
		}
	}
	for (int i = 23; i <= 400; i++)
	{
		if (prime_list[i] == 0)v.push_back(i);
	}

	for (int i = 0; i < v.size(); i++)
	{
		int a = v[i];
		for (int j = 400; j <= 1000; j++)
		{
			if (a != j && (j % a == 0))
			{
				prime_list[j] = 1;
			}
		}
	}
	for (int i = 401; i <= 1000; i++)
	{
		if (prime_list[i] == 0)v.push_back(i);
	}



	for (int i = 0; i < v.size(); i++)
	{
		int a = v[i];
		for (int j = 1001; j < 1000001; j++)
		{
			if (a != j && (j%a == 0))
			{
				prime_list[j] = 1;
			}
		}
	}


	int a, b;
	while (cin >> a)
	{
		if (a == 0)break;
		for (b = 3;  ; b++)
		{
			if (prime_list[b] == 0 && prime_list[a - b] == 0)
			{
				cout << a << " = " << b << " + " << a - b << endl;
				break;
			}
		}
	}
	return 0;
}