Generate the Cartesian Product of 2 vectors In-Place?

Question

If I want to get the Cartesian Product of these two vectors:

vector final{\"a\",\"b\",\"c\"};
vector temp{         


        

Answer 1

This is just a personal preference option to Vald from Moscow's solution. I think it may be faster for dynamic arrays because there would be less branching. But I haven't gotten around to writing a timing test bench.

Given the inputs vector final and vector temp:

const auto size = testValues1.first.size();

testValues1.first.resize(size * testValues1.second.size());

for (int i = testValues1.first.size() - 1; i >= 0; --i){
    testValues1.first[i] = testValues1.first[i % size] + testValues1.second[i / size];
}

EDIT:

Nope, this solution is slower not faster: http://ideone.com/e.js/kVIttT

And usually significantly faster, though I don't know why...

In any case, prefer Vlad from Moscow's answer