C++ <deque> - cbegin() Function

The C++ deque::cbegin function returns the constant iterator (const_iterator) pointing to the first element of the deque. Please note that, Unlike the deque::front function, which returns a direct reference to the first element, it returns the const_iterator pointing to the same element of the deque.

Note: A const_iterator is an iterator that points to constant value. The difference between iterator and const_iterator is that the const_iterator cannot be used to modify the content it points to, even if the deque element is not itself constant.

Syntax

• C++11

const_iterator cbegin() const noexcept;

Parameters

No parameter is required.

Return Value

A const_iterator to the beginning of the sequence container.

Time Complexity

Constant i.e, Θ(1).

Example:

In the example below, the deque::cbegin. function returns the const_iterator pointing to the first element of the deque called MyDeque.

#include <iostream>
#include <deque>
using namespace std;
 
int main (){
  deque<string> MyDeque{"Alpha","Coding","Skills"};
  deque<string>::const_iterator cit;

  cit = MyDeque.cbegin();
  cout<<*cit<<" ";
  cit++;
  cout<<*cit<<" ";
  cit++;
  cout<<*cit<<" ";
  return 0;
}

The output of the above code will be:

Alpha Coding Skills

Example:

Lets see another example where the deque called MyDeque contains integer values and deque::cbegin function is used with deque::cend function to specify a range including all elements of the deque container.

#include <iostream>
#include <deque>
using namespace std;
 
int main (){
  deque<int> MyDeque{10, 20, 30, 40, 50};
  deque<int>::const_iterator cit;

  for(cit = MyDeque.cbegin(); cit != MyDeque.cend(); ++cit)
    cout<<*cit<<" ";

  return 0;
}

The output of the above code will be:

10 20 30 40 50