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C++ multimap::cbegin() Function

The C++ std::multimap::cbegin() function is used to return a constant iterator to the first element in the multimap, enabling read-only access to its elements. Unlike begin() function, which returns a mutable iterator, cbegin() function ensures that the data cannot be modified, increasing safe iteration over its elements. The time complexity of this function is constant i.e.O(1).

Following is the syntax for std::multimap::cbegin() function.

const_iterator cbegin() const noexcept;

This function does not accepts any parameter.

This function returns a constant iterator pointing to the first element.

Let's look at the following example, where we are going to use the cbegin() function and accessing the first element.

#include <iostream>
#include <map>
int main()
{
    std::multimap<int, std::string> a = {{1, "Welcome"}, {2, "Hi"}, {3, "Hello"}};
    auto it = a.cbegin();
    std::cout << " " << it->first << ": " << it->second << std::endl;
    return 0;
}

Output of the above code is as follows −

1: Welcome

Consider the following example, where we are going to find the specific element using cbegin() function.

#include <iostream>
#include <map>
int main()
{
    std::multimap<int, std::string> a = {{1, "Hi"}, {2, "Hello"}, {3, "Namaste"}};
    auto x = a.cbegin();
    while (x != a.cend() && x->first != 3) {
        ++x;
    }
    if (x != a.cend()) {
        std::cout << "Element found: " << x->second << std::endl;
    } else {
        std::cout << "Element not found." << std::endl;
    }
    return 0;
}

Following is the output of the above code −

Element found: Namaste

In the following example, we are going to iterate through the multimap using the cbegin() function.

#include <iostream>
#include <map>
int main()
{
    std::multimap<int, std::string> a = {{1, "TutorialsPoint"}, {2, "TP"}, {3, "Tutorix"}};
    for(auto x = a.cbegin(); x != a.cend(); ++x) {
        std::cout << x->first << ": " << x->second << std::endl;
    }
    return 0;
}

If we run the above code it will generate the following output −

1: TutorialsPoint
2: TP
3: Tutorix

multimap.htm

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