C++ List::rend() Function

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The C++ std::list::rend() function is used to retrieve a reverse iterator to the element following the last element of the reversed list.

This function corresponds to the element preceding the first element of the non-reversed list. The elements of this list act as a placeholder, attempting to access it results in undefined behavior. In C++, iterators are used to point at the memory addresses of STL(standard template library) containers.

The rend() function is similar to the crend() function, where the crend() function returns a constant reverse iterator to the element following the last element of the reversed list, whereas the rend() function returns a reverse iterator following to the last element of the reversed list.

Syntax

Following is the syntax of the C++ std::list::rend() function −

const_reverse_iterator rend();

Parameters

• It does not accept any parameter.

Return Value

This function returns a reverse iterator to the element following the last element of the reversed list.

Example 1

In the following program, we are using the C++ std::list::rend() function to retrieve a reverse iterator to the element following the last element of the current list {10, 20, 30, 40}.

#include<iostream>
#include<list>
using namespace std;

int main() {
   //create a list
   list<int> num_list = {10, 20, 30, 40};
   cout<<"List elements are: ";
   for(int n : num_list) {
      cout<<n<<" ";
   }
   auto it = num_list.rend();
   cout<<"\nA reverse iterator of the last element: ";
   cout<<*it;
}

Output

Following is the output of the above program −

List elements are: 10 20 30 40 
A constant reverse iterator of the last element: 4

Example 2

Apart from the int-type list element, you can also retrieve an iterator of any other type list element like char and string list content.

Following is another example of the C++ std::list::rend() function. Here, we are creating a list(type char) named symbols with the values {'@', '#', '$', '%', '&', '*'}. Then using the rend() function, we are trying to retrieve a reverse iterator following to the last element of the reversed list.

#include<iostream>
#include<list>
using namespace std;

int main() {
   //create a list
   list<char> symbols  = {'@', '#', '$', '%', '&', '*'};
   cout<<"List elements are: ";
   for(char v : symbols) {
      cout<<v<<" ";
   }
   auto it = symbols.rend();
   cout<<"\nA reverse iterator of the last element: ";
   cout<<*it;
}

Output

This will generate the following output −

List elements are: @ # $ % & * 
A reverse iterator of the last element: 

Example 3

If the list type is a string.

In this example, we are creating a list(type string) named names with the values {"Mukesh", "Rahul", "Mohan", "Shavita"}. Then, using the rend() function, we are trying to retrieve a reverse iterator following to the last element of the reversed list.

#include<iostream>
#include<list>
using namespace std;

int main() {
   //create a list
   list<string> names = {"Mukesh", "Rahul", "Mohan", "Shavita"};
   cout<<"List elements are: ";
   for(string s : names ) {
      cout<<s<<" ";
   }
   auto it = names.rend();
   cout<<"\nA reverse iterator of the last element: ";
   cout<<*it;
}

Output

The above program produces the following output −

List elements are: Mukesh Rahul Mohan Shavita 
A reverse iterator of the last element: 
Segmentation fault

Example 4

Using for loop along with the rend() function to retrieve a reverse iterator of the reversed list.

In this example, we use the rend() function along with the for loop to loop through the current container {1, 2, 3, 4 ,5, 6, 7, 8, 9, 10} and retrieve a reverse iterator of all elements of the reversed list.

#include<iostream>
#include<list>
using namespace std;

int main() {
   //create a list
   list<int> num_list = {1, 2, 3, 4 ,5, 6, 7, 8, 9, 10} ;
   cout<<"List elements are: ";
   for(int n : num_list) {
      cout<<n<<" ";
   }
   cout<<"\nThe reverse iterator of an elements are : ";
   for (auto it = num_list.crbegin(); it != num_list.rend(); it++) {
      cout<<*it<<" ";
   }
}

Output

On executing the above program, it will produce the following output −

List elements are: 1 2 3 4 5 6 7 8 9 10 
The reverse iterator of an elements are : 10 9 8 7 6 5 4 3 2 1