All sub-strings of a string

#include <iostream>
#include <iomanip>
#include <map>
#include <string>
#include <conio.h>

/*
Print all the substrings of a given string. 
Is there any solution better than O(2^n)
*/
std::map<std::string, int> substrings;
std::map<std::string, int>::iterator it;

/*
A O(2^n) algorithm !

recurrence: T(n) = 2T(n-1)
*/
void subStrings(std::string s)
{
    int slice = s.length()-1;
    
    // add string to substrings 
    substrings[s] = 1;
    
    if(slice == 0) return; // base case ! single character
    
    int pos = 0;
    while(true)
    {
        std::string tmp = s.substr(pos, slice);
        subStrings(tmp);
        pos++;
        if(pos+slice > s.length()) break;        
    }
}

/*
A O(n^2) algorithm - bubble sort like explanation
*/
void subStrings1(std::string s)
{
    for(int i = 0; i < s.length(); i++)
    {
        for(int j = 1; j <= s.length()-i; j++)
            std::cout << s.substr(i,j) << std::endl;
    }
}

int main()
{
    std::string s = "ABCDEF";
    subStrings(s);
    
    for(it = substrings.begin(); it != substrings.end(); it++)
        std::cout << (*it).first << std::endl;
    
    subStrings1(s);
    
    getch();
}