Need help.

[toadmar]

I have code to write to a csv file. The code gives me a file that looks like this;

aaaa
aaab
aaac
aaad

and so on.

i would like to make it so that there can be no more than two of the same characters next to each other.

so that i would get.

aaba
aaca
abca
abba
acca
baac.

here is the code:

#include "stdafx.h"
#include <fstream>
#include <algorithm>
#include <cassert>
#include <iostream>
#include <vector>
#include <stdio.h>
#include <time.h>

using std::copy;
using std::cout;
using std::endl;
using std::vector;
using namespace std;

ofstream myfile;


		
void combinations_r_recursive(const vector<char> &elems, unsigned long req_len,
	vector<unsigned long> &pos, unsigned long depth,
	unsigned long margin)
{	
	// Have we selected the number of required elements?
	if (depth >= req_len)
	{	
		
		for (unsigned long ii = 0; ii < pos.size(); ++ii)
			
			myfile << elems[pos[ii]];
			myfile << "," << endl;
			cout << ". ";
			
		return;
	}	
	// Try to select new elements to the right of the last selected one.
	for (unsigned long ii = margin; ii < elems.size(); ++ii)
	{		
		pos[depth] = ii;
		combinations_r_recursive(elems, req_len, pos, depth + 1, ii);
	}
	
	return;
}

void combinations_r(const vector<char> &elems, unsigned long req_len)
{	
	assert(req_len > 0 && req_len <= elems.size());
	vector<unsigned long> positions(req_len, 0);
	combinations_r_recursive(elems, req_len, positions, 0, 0);
}
const unsigned long num_elements = 36;
const unsigned long comb_len = 3;

int main()
{	
	clock_t start = clock();
	myfile.open ("toddkeyfile.csv");
	vector<char> elements(num_elements);
	char elements_str[num_elements + 1] = "abcdefghijklmnopqrstuvwxyz1234567890";
	copy(elements_str, elements_str + num_elements, elements.begin());
	combinations_r(elements, comb_len);
	myfile.close();
	printf("Time Elasped: %f\n",(double)clock() - start);
	system("Pause");
	return 0;
	
}

thanks for any help you can give me.

[toadmar]

I found another problem with the code.

I need help to fix:
it writes out
aaa
aab
aac
aad
...
abb when it get to "ab_" it go abb it skip aba. i need aba
abc
abd
...
acc when it get to "ac_" again it skip aca and acb
acd
ace
acf
acg
ach


Thanks for any help you can give me.