map key_comp() function in C++ STL

The map::key_comp() is a function in STL in C++ that returns a copy of comparison object used by container that compare keys.

Syntax:

map.key_comp()

Return value: This method returns the comparison object used by container that compare keys.

Below examples illustrate the working of key_comp() method:

Example:



filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ program to demonstrate map::key_comp().
  
#include <iostream>
#include <map>
using namespace std;
  
int main()
{
    // Declare the map
    map<char, int> mymap;
  
    // Compare the key.
    map<char, int>::key_compare
        mycomp
        = mymap.key_comp();
  
    // Populate the map
    mymap['x'] = 50;
    mymap['y'] = 100;
    mymap['z'] = 150;
  
    // Print the map
    cout << "mymap contain:\n";
  
    char highest = mymap.rbegin()->first;
  
    // key value of last element
    map<char, int>::iterator
        it
        = mymap.begin();
  
    do {
        cout << it->first
             << " => " << it->second
             << "\n";
    } while (mycomp((*it++).first, highest));
  
    cout << "\n";
  
    return 0;
}

chevron_right


Output:

mymap contain:
x => 50
y => 100
z => 150

Example 2:

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ program to demonstrate map::key_comp().
  
#include <iostream>
#include <map>
using namespace std;
  
int main()
{
    // Declare the map
    map<char, int> mymap;
  
    // Compare the key.
    map<char, int>::key_compare
        mycomp
        = mymap.key_comp();
  
    mymap['a'] = 100;
    mymap['b'] = 200;
    mymap['c'] = 300;
  
    cout << "mymap contain:\n";
  
    char highest = mymap.rbegin()->first;
  
    // key value of last element
  
    map<char, int>::iterator
        it
        = mymap.begin();
  
    do {
        cout << it->first
             << " => "
             << it->second
             << '\n';
    } while (mycomp((*it++).first, highest));
  
    cout << '\n';
  
    return 0;
}

chevron_right


Output:

mymap contain:
a => 100
b => 200
c => 300


My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.




Article Tags :
Practice Tags :


Be the First to upvote.


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.