1 - 1+2 - 1+2+3 - 1+2+3+4 - 1+2+3+4+5
|   |     |       |
|   |     |       1+2+3+5
|   |     |
|   |     1+2+4 - 1+2+4+5
|   |     |
|   |     1+2+5
|   |
|   1+3 - 1+3+4 - 1+3+4+5
|   |     |
|   |     1+3+5
|   |
|   1+4 - 1+4+5
|   |
|   1+5
|
2 - 2+3 - 2+3+4 - 2+3+4+5
|   |     |
|   |     2+3+5
|   |
|   2+4 - 2+4+5
|   |
|   2+5
|
3 - 3+4 - 3+4+5
|   |
|   3+5
|
4 - 4+5
|
5            

#include <iostream>
#include <iomanip>
#include <fstream>
#include <ctime>

using namespace std;

const int n =  20 ;
const int nums[n] = { 1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  10 ,  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  10 };

int count =  0 ;
ofstream outfile("output.txt", ios::out | ios::trunc);

void stepIn(int pos, int sum)
{
	for(int i = pos; i < n; i++)
	{
		int new_sum = sum + nums[i];
		outfile << setw( 10 ) << new_sum;
		count++;
		if(i < n -  1 ) stepIn(i +  1 , new_sum);
	}
}

int main()
{
	time_t timestamp;
	time(&timestamp);
	outfile << "Started at " << ctime(&timestamp) << endl;

	stepIn( 0 ,  0 );

	timestamp = time(NULL) - timestamp;
	outfile << endl << endl << "Total combinations: " << count << endl;
	outfile << "Process duration: " << timestamp << " sec" << endl;

	return  0 ;
}

outfile << new_sum << endl;