C++ Deque::cbegin() Function

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The C++ std::deque::cbegin() function is used to return a constant iterator pointing to the first element, allowing the read-only access without modifying the container. This is useful for iterating through elements in a deque while ensuring they remain unchanged. It provides a way to access elements from the beginning of the deque in a safe and non-modifiable manner.

Syntax

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

const_iterator cbegin() const noexcept;

Parameters

It does not accepts any parameters.

Return value

This function returns a const_iterator to the beginning of the sequence.

Exceptions

This function never throws exception.

Time complexity

The time complexity of this function is Constant i.e. O(1)

Example

In the following example, we are going to consider the basic usage of cbegin() function.

#include <iostream>
#include <deque>
int main()
{
    std::deque<char> x = {'A', 'B', 'C', 'D'};
    auto a = x.cbegin();
    while (a != x.cend()) {
        std::cout << *a << " ";
        ++a;
    }
    return 0;
}

Output

Output of the above code is as follows −

A B C D 

Example

Consider the following example, where we are going to access the first element using cbegin() function

#include <iostream>
#include <deque>
int main()
{
    std::deque<std::string> a = {"TutorialsPoint", "Tutorix", "TP"};
    std::cout << " " << *a.cbegin() << std::endl;
    return 0;
}

Output

Following is the output of the above code −

TutorialsPoint

Example

In the following example, we are going to use the cbegin() function to get the constant iterator and compare the first element with the value.

#include <iostream>
#include <deque>
int main()
{
    std::deque<char> a = {'A', 'B', 'C', 'D'};
    auto x = a.cbegin();
    if (*x == 'A') {
        std::cout << "First Element is equal to given value." << std::endl;
    } else {
        std::cout << "First Element is not equal to given value." << std::endl;
    }
    return 0;
}

Output

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

First Element is equal to given value.