Arbitrary number of nested-loops? [duplicate]

Answer 1

The recursive way ...

void Recurse(const vector>& v, 
             size_t listToTwiddle, 
             vector& currentPermutation)
{
    // terminate recursion
    if (listToTwiddle == v.size())
    {
        for(auto i = currentPermutation.cbegin(); i != currentPermutation.cend(); ++i)
        {
            cout << *i << " ";
        }
        cout << endl;
        return;
    }

    for(size_t i = 0; i < v[listToTwiddle].size(); ++i)
    {
        // pick a number from the current list
        currentPermutation.push_back(v[listToTwiddle][i]);

        // get all permutations having fixed this number
        Recurse(v, listToTwiddle + 1, currentPermutation);

        // restore back to original state
        currentPermutation.pop_back();
    }
}

void Do(const vector>& v)
{
    vector permutation;
    Recurse(v, 0, permutation);
}