void 可表示的数（数组前面2个数的和）()
{
	int aa[]{1,2,3,4,5,6,7,8,9}, j = 0, z = 1, jj = z, n = 9, ge = 0;
	string a = "";
	while (j < n)//缘由https://bbs.csdn.net/topics/396063706?page=1#post-410898529
	{
		if (++jj < n)
		if (aa[j] + aa[z] == aa[jj])
		if (a.find(to_string(aa[jj])) == string::npos)
			++ge, cout << aa[j] << "+" << aa[z] << "=" << aa[jj] << ends, a.push_back(aa[jj] + '0'), a += ","; else 0; else 0;
		else if (++z >= n)
			jj = z = ++j + 1;
		else jj = z;
	}
	cout << ge;
}

int aa[]{1,2,3,4,5,6,7,8,9}

 假如不限制重复的话