How to get all possible binary numbers in a vector - binaryfiles

Question

I'm looking for a way to generate all possible binary combinations and insert that into a vector of strings.
For example, if I have n=3, I would like to create a string of vectors that contains all the possible combinations from ["000", ..., "111"].
I have created a code that can generate binary strings of the values.
std::vector<std::string> get_combs(std::vector<std::string> vector, const int Z){
//I'm not sure why this line causes the error
constexpr size_t N = Z;
for(size_t i=0; i<(1<<N); ++i) {
std::bitset<N> bs = i;
vec.push_back(bs.to_string());
}
return vec;
}
// Driver Code
int main()
{
int Z = 2;
std::vector<std::string> values;
values = get_combs(values, const int Z);
}
But right now it's just printing as 0 0 0 1 1 0 1 1

Answer 1

A non-recursive converting version (loop over all the numbers and convert them to strings of binary digits):
std::string to_binstring(int x, int width)
{
std::string s(width, '0');
for (int i = 0; i < width; i++)
{
s[i] = '0' + x % 2;
x /= 2;
}
std::reverse(s.begin(), s.end());
return s;
}
std::vector<std::string> all_binstrings(int width)
{
const unsigned int limit = 1 << width;
std::vector<std::string> bins;
for (unsigned int i = 0; i < limit; i++)
{
bins.push_back(to_binstring(i, width));
}
return bins;
}
A recursive string-building version (attach '0' and '1' to all of the shorter strings):
std::vector<std::string> recursive_binstrings(int width)
{
if (width == 1)
{
return {"0", "1"};
}
std::vector<std::string> rest = recursive_binstrings(width-1);
std::vector<std::string> appended;
for (const auto& s: rest)
{
appended.push_back(s + '0');
appended.push_back(s + '1');
}
return appended;
}

Answer 2

Is N known at compile-time? If so std::bitset<N> could be useful:
#include <iostream>
#include <bitset>
#include <vector>
using namespace std;
int main()
{
constexpr size_t N = 3;
std::vector<std::string> vec;
for (size_t i=0; i<(1<<N); ++i) {
std::bitset<N> bs = i;
vec.push_back(bs.to_string());
}
// Prints "000 001 010 011 100 101 110 111"
for (auto& elem: vec) cout << elem << ' ';
cout << endl;
return 0;
}
https://godbolt.org/z/WxWz43