Question

I have a problem iterating over the second map in a map.

#include <map>

using namespace std;

map<string, map<string, string> > mymap;
map<string, map<string, string> >::iterator itm;
pair<map<string, map<string, string> >::iterator,bool> retm;

for( itm=mymap.begin(); itm!=mymap.end(); ++itm)
{
cout << "first:\t" << it->first << endl;
}

How can I iterate over the second map and get both first and second keys/values?

And the second question is, how can I “insert” into the first and second map using the “insert” function that comes with maps?

I hope someone has a full answer.

Answer 1

#include <map>
#include <iostream>
using namespace std;

map<string, map<string, string> > mymap;
map<string, map<string, string> >::iterator itm;
pair<map<string, map<string, string> >::iterator,bool> retm;

int main() {

  /* populate: */
  mymap.insert(make_pair ("something", map<string, string>()));
  mymap["something"].insert(make_pair ("2", "two"));

  /* traverse: */
  for( itm=mymap.begin(); itm!=mymap.end(); ++itm)
  {
    cout << "first:\t" << itm->first << endl;

    for (map<string, string>::iterator inner_it = (*itm).second.begin();
        inner_it != (*itm).second.end(); 
        inner_it++) {
      cout << (*inner_it).first << " => " << (*inner_it).second << endl;
    }   

  }

  return 0;
}