Interleaving/deinterleaving 3 vectors in C++ STL

Answer 1

I'm not sure about interleaving but you can use for_each to deinterleave. You would still want to add additional error checking (that the source size is correct etc):

#include <iostream>
#include <vector>

typedef std::vector<double> dVector;
typedef dVector::iterator dVectorIT;

class DeInterleave
{
public:
    DeInterleave(std::vector<dVector>& output) : output_(output), currentIndex_(0) { }
    void operator()(const dVector::value_type& item)
    {
        output_[currentIndex_].push_back(item);
        currentIndex_ = (currentIndex_ + 1) % output_.size();
    }

private:
    std::vector<dVector>& output_;
    int currentIndex_;
};

int main()
{
    dVector source;
    source.push_back(5.0);
    source.push_back(6.0);
    source.push_back(8.0);
    source.push_back(2.0);
    source.push_back(2.0);
    source.push_back(1.0);
    std::vector<dVector> dest(3);

    std::for_each(source.begin(), source.end(), DeInterleave(dest));

    std::cout << dest[0].size() << " " << dest[0][0] << ":" << dest[0][1] << std::endl;
    std::cout << dest[1].size() << " " << dest[1][0] << ":" << dest[1][1] << std::endl;
    std::cout << dest[2].size() << " " << dest[2][0] << ":" << dest[2][1] << std::endl;

    return 0;
}