the different combinations of a vector's values

Question

Suppose I have a vector of n values, I want to get the different combinations of its values, for example: if I have vect = [a, b, c] the different combinations that I want are: [a, b, c], [a,b], [a,c], [b,c], [a], [b], [c]

Note that for example [a,b] is the same as [b,a] so I don't need to keep both of them.

Answer 1

Count from 0 to 2^vector.size() - 1. If bit i of your loop variable is 1, include vector[i] in your combination.

vector<char> v;
v.push_back('a');
v.push_back('b');
v.push_back('c');
for (int counter = 0; counter < (1 << v.size()); ++counter)
{
    vector<char> combination;
    for (int i = 0; i < v.size(); ++i)
    {
        if (counter & (1 << i))
            combination.push_back(v[i]);
    }

    // do something with combination
}

Edit: if you want to exclude the empty set, start counting at 1.