go through map c++

Question

So, I have an std::map<int, my_vector> and I want to go through each int and analyse the vector. I haven't gotten to the part of analyzing the vector just yet, I'm still trying to figure out how to go through every single element on the map. I know it is possible to have an iterator, but I didn't quite understood how it works, also, I don't know if there isn't a better way to do what I intend to do

Answer 1

You can simply iterate over the map. Each map element is an std::pair<key, mapped_type>, so first gives you the key, second the element.

std::map<int, my_vector> m = ....;
for (std::map<int, my_vector>::const_iterator it = m.begin(); it != m.end(); ++it)
{
  //it-->first gives you the key (int)
  //it->second gives you the mapped element (vector)
}

// C++11 range based for loop
for (const auto& elem : m)
{
  //elem.first gives you the key (int)
  //elem.second gives you the mapped element (vector)
}

Answer 2

Iterators are the perfect thing for this. Look around http://www.cplusplus.com/reference/map/map/begin/