How to change this code?

#include <iostream>
#include <string.h> // for strlen
#include <stdlib.h> // for atoi
#include <sstream>
void expand_combinations(const char *remaining_string, std::ostringstream& i, int remain_depth)
{
    if(remain_depth==0)
    {
        std::cout << i.str() << std::endl;
        return;
    }

    for(int k=0; k < strlen(remaining_string); ++k)
    {
        std::ostringstream l;
        l << i.str();
       开发者_C百科 l << remaining_string[k];
        expand_combinations(remaining_string+k+1, l, remain_depth - 1);
    }
    return;
}
int main(int argc, char **argv)
{
    std::ostringstream i;
    if(argc<3) return 1;
    expand_combinations(argv[1], i, atoi(argv[2]));
    return 0;
}

How can this code be changed so that it doesn't use ostringstream?

The following is your code with string in place of ostringstream. Normally I'd refactor the code but since your question was pretty specific I'll leave it alone.

#include <iostream>
#include <string>
#include <stdlib.h>

using namespace std;

void expand_combinations(const char *remaining_string, string const & s, int remain_depth)
{
    if(remain_depth==0)
    {
        std::cout << s << std::endl;
        return;
    }

    for(int k=0; k < strlen(remaining_string); ++k)
    {
        string str(s);
        str.append(1, remaining_string[k]);
        expand_combinations(remaining_string+k+1, str, remain_depth - 1);
    }
    return;
}

int main(int argc, char **argv)
{
    if(argc<3) return 1;
    expand_combinations(argv[1], "", atoi(argv[2]));
    return 0;
}