bin_str.c

#include <stdio.h>
#include <string.h>

void find_variants(char *input, char* working, int size);
void bin_str_func(char *input);

int main(int argc, char *argv[])
{
    bin_str_func(argv[1]);
    return 0;
}

void bin_str_func(char *input)
{
    int length;
    length = strlen(input);
    char *working = malloc(length * sizeof(char));
    find_variants(input, working, length);
}

void find_variants(char *input, char* working, int size)
{
    if(*input == '\0') printf("%s\n", &working[-size]);
    else
    {
        if(*input == 'x')
        {
            char* w_branch = working;
            char* i_branch = input;
            *working = '0';
            find_variants(++input, ++working, size);
            working = w_branch;
            input = i_branch;
            *working = '1';
            find_variants(++input, ++working, size);            
        }
        else
        {
            *working = *input;
            find_variants(++input, ++working, size);
        }
    }
}