map cbegin() and cend() function in C++ STL

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

    Syntax:

    map_name.cbegin()
    

    Parameters: The function does not accept any parameter.

    Return Value: The function returns a constant iterator referring to the first element in the map container.

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    // C++ program to illustrate
    // the map::cbegin() function
    #include <bits/stdc++.h>
    using namespace std;
      
    int main()
    {
      
        // initialize container
        map<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.cbegin();
      
        cout << "The first element is: ";
        cout << "{" << ite->first << ", "
             << ite->second << "}\n";
      
        // prints the elements
        cout << "\nThe map is : \n";
        cout << "KEY\tELEMENT\n";
        for (auto itr = mp.cbegin(); itr != mp.cend(); ++itr) {
            cout << itr->first
                 << '\t' << itr->second << '\n';
        }
        return 0;
    }
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    Output:
    The first element is: {1, 40}
    
    The map is : 
    KEY    ELEMENT
    1    40
    2    30
    3    60
    4    20
    5    50
    
  2. map::cend() is a built-in function in C++ STL which returns a constant iterator pointing to the theoretical element that follows last element in the multimap. Since map container contains the element in an ordered way, cend() will point to that follows the last element according to the container’s sorting criterion.

    Syntax:



    map_name.cend()
    

    Parameters: The function does not accept any parameter.

    Return Value: The function returns a constant iterator pointing to the theoretical element that follows the last element in the map.

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    // C++ program to illustrate
    // the map::cend() function
    #include <bits/stdc++.h>
    using namespace std;
      
    int main()
    {
      
        // initialize container
        map<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 });
      
        // print the elements
        cout << "\nThe map is : \n";
        cout << "KEY\tELEMENT\n";
        for (auto itr = mp.cbegin(); itr != mp.cend(); ++itr) {
            cout << itr->first
                 << '\t' << itr->second << '\n';
        }
        return 0;
    }
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    Output:
    The map is : 
    KEY    ELEMENT
    1    40
    2    30
    3    60
    4    20
    5    50
    

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