sorting in std::map where key is a std::string

Question

I have a std::map mymap

Now, if I insert values in the map like:

std::map <string, string> mymap; mymap["first"] = "hi"; mymap["third"] = "how r you"; mymap["second"] = "hello"; 

Now I want to iterate over the map and print the value in sorted(keys) manner:

map<string, string>::iterator itr; for(itr = mymap.begin(); itr != mymap.end(); itr++) {    string newline = itr->second;    cout << newline << endl; } 

Output should be:

hi  hello  how r you  

I thought that by default map stores in sorted keys manner but I'm getting the same order in output as I'm giving in input. Do I need to provide my sort function for this or need to do something extra before iterating over the map?

Answer 1

The elements in std::map are ordered (by default) by operator< applied to the key.

The code you posted, with minor edits, worked for me as you expected:

std::map <string, string> mymap; mymap["first"]="hi"; mymap["third"]="how r you"; mymap["second"]="hello";  for (std::map<string, string>::iterator i = mymap.begin(); i != mymap.end(); i++) {     cout << i->second << "\n"; } 

Prints:

hi hello how r you