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multimap::crbegin() and multimap::crend() in C++ STL

  1. multimap::crbegin() is a built-in function in C++ STL which returns a constant reverse iterator referring to the last element in the multimap container. Since multimap container contains the element in an ordered way, crbegin() will point to that element that will come last according to the container’s sorting criterion.

    Syntax:

    multimap_name.crbegin()
    

    Parameters: The function does not accept any parameter.

    Return Value: The function returns a constant reverse iterator referring to the last element in the multimap container.

    // C++ program to illustrate 
    // multiset::crbegin() function
    #include <bits/stdc++.h>
    using namespace std;
      
    int main()
    {
      
        // initialize container
        multimap<int, int> mp;
      
        // insert elements in random order
        mp.insert({ 2, 30 });
        mp.insert({ 1, 40 });
        mp.insert({ 3, 60 });
        mp.insert({ 4, 20 });
        mp.insert({ 5, 50 });
      
        auto ite = mp.crbegin();
        cout << "The last element is {" << ite->first 
        << ", " << ite->second << "} ";
      
        // prints the elements
        cout << " The multimap in reverse order is: ";
        cout << "KEY ELEMENT ";
        for (auto itr = mp.crbegin(); itr != mp.crend(); ++itr) {
            cout << itr->first
                 << ' ' << itr->second << ' ';
        }
        return 0;
    }

    Output:

    The last element is {5, 50}
    
    The multimap in reverse order is: 
    KEY    ELEMENT
    5    50
    4    20
    3    60
    2    30
    1    40
    
  2. multimap::crend() is a built-in function in C++ STL which returns a constant reverse iterator pointing to the theoretical element before the first element in the multimap. Since multimap container contains the element in an ordered way, crend() will point to the element theoretically before the first element according to the container’s sorting criterion.

    Syntax:



    multimap_name.crend()
    

    Parameters: The function does not accept any parameter.

    Return Value: The function returns a constant reverse iterator pointing to the theoretical element before the first element in the multimap.

    // C++ program to illustrate 
    // multiset::crend() function
    #include <bits/stdc++.h>
    using namespace std;
      
    int main()
    {
      
        // initialize container
        multimap<int, int> mp;
      
        // insert elements in random order
        mp.insert({ 2, 30 });
        mp.insert({ 1, 40 });
        mp.insert({ 3, 60 });
        mp.insert({ 4, 20 });
        mp.insert({ 5, 50 });
      
        // prints the elements
        cout << " The multimap in reverse order is : ";
        cout << "KEY ELEMENT ";
        for (auto itr = mp.crbegin(); itr != mp.crend(); ++itr) {
            cout << itr->first
                 << ' ' << itr->second << ' ';
        }
        return 0;
    }

    Output:

    The multimap in reverse order is : 
    KEY    ELEMENT
    5    50
    4    20
    3    60
    2    30
    1    40
    


This article is attributed to GeeksforGeeks.org

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