How to Sort STL Map in C++ in Increasing Order according to its Key Value?

By default std::map is already sorted in increasing order. The third template parameter of a std::map, is a Compare functor wich is equal to std::less

By default std::map is already sorted in increasing order. The third template parameter of a std::map, is a Compare functor wich is equal to std::less, if you want on the other hand decreasing order use std::greater for the third template parameter.

e.g :

std::map<int, int, std::greater> m;

I wonder how can I implement the STL map sorting by value.

For example, I have a map m

and then.. I'd like to sort that with the m's value. So, if I print the map, I'd like to get the result like

this.