main.cpp

int main()
{
        ifstream in1("in1.txt");
	vector<int> mas;
	int r=0; int m=0;
	while(!in1.eof())
	{
		in1>>m;
		mas.push_back(m);
		r++;
	}
	in1.close();
	int x;
	bool var;
	cout<<"Please, type number. 0- Sorting ascending, 1- Sorting in decreasing order. \n";
	cin>>var;
	if (var==0) {sort(mas.begin(), mas.end());}
	else if (var==1) {sort(mas.end(), mas.begin());}
	ofstream out1("out1.txt");
	for (vector<int>::iterator it=mas.begin(); it!=mas.end(); it++)cout<<" "<<*it;
        return 0;
}

line 5, unuser variable r.

Oh, use in line 10, but don't anything good.

Container vector have method size.