In the C++ programming language, the deque is a sequence container, which is a part of the Standard Template Library (STL). The deque enables us to insert or delete elements from both the front and back. The rend function is the member function of the deque container, which provides access to elements held by that deque container.
In C++ , the rend function is commonly used to return a reverse iterator thacpp tutorials to the theoretical element that precedes the first element of the deque . In this way, it can be used in conjunction with rbegin to iterate or manipulate the deque in reverse order. It is mostly used in reverse iteration loops and algorithms involving reverse iterators, such as std::reverse, std::find, std::sort, and many other functions. The deque rend function can be defined in the <deque> header file.
Syntax:
It has the following syntax:
reverse_iterator rend();
const_reverse_iterator rend() const noexcept;
In these syntaxes,
reverse_iterator rend;
- It is used to return a reverse iterator pointing to the element before the first element of the deque.
- It is commonly utilized with non-constant (modifiable) deques.
constreverseiterator rend const noexcept;
- It is used to return a constant reverse iterator that refers to the same spot (before the first element).
- It is commonly utilized with constant deques where elements cannot be modified.
C++ Simple deque rend Function Example
Let us take an example to illustrate the deque rend function in C++.
Example
#include <iostream>
#include <deque>
using namespace std; //using standard namespace
int main() { //main function
// Create a deque and insert elements
deque<int> numbers = {10, 20, 30, 40, 50};
cout << "Elements of deque in reverse order: ";
// Using reverse iterators rbegin() and rend()
for (auto it = numbers.rbegin(); it != numbers.rend(); ++it) {
cout << *it << " ";
}
cout << endl;
return 0;
}
Output:
Elements of deque in reverse order: 50 40 30 20 10
Explanation:
In this example, we have taken an integer deque that is initialized with the elements {10, 20, 30, 40, 50}. After that, we use the rbegin function that returns a reverse iterator pointing to the last element of a sequence (50 in this case). Finally, it prints the deque elements from first to last: 50 40 30 20 10.
C++ the deque::rend function Example for Reverse Searching and Traversal
Let us take an example to illustrate the deque rend function to reverse search and traverse the characters in C++.
Example
#include <iostream>
#include <deque>
#include <algorithm> // for find
using namespace std; //using standard namespace
int main() { //main function
// Create a deque of characters
deque<char> letters = {'A', 'B', 'C', 'D', 'E'};
cout << "Deque elements: ";
for (char ch : letters)
cout << ch << " ";
cout << endl;
// Find a specific element ('C') using reverse iterators
auto it = find(letters.rbegin(), letters.rend(), 'C');
if (it != letters.rend()) {
cout << "Element found in reverse traversal: " << *it << endl;
cout << "Elements before 'C' in reverse order: ";
for (auto itr = letters.rbegin(); itr != it; ++itr) {
cout << *itr << " ";
}
cout << endl;
} else {
cout << "Element not found!" << endl;
}
return 0;
}
Output:
Deque elements: A B C D E
Element found in reverse traversal: C
Elements before 'C' in reverse order: E D
Explanation:
In this example, we have created a deque of characters that is initialized with the characters {'A', 'B', 'C', 'D', 'E'}. After that, we have utilized the find iterator with the reverse iterators rbegin and rend functions to get the character 'C' from the end toward the start. When we find the C in the program, it displays all the elements that appear before C in the reverse order. Finally, the loop prints the elements in the output (E, D).
Features of the Deque rend Function in C++
There are several features of the deque rend function in C++. Some of them are as follows:
- In the C++ programming language, the deque rend function is commonly utilized to return the reverse iterator pointing to the theoretical element before the first element of the deque.
- We can utilize the deque rend function in C++ to iterate via a deque in the reverse order.
- It is commonly utilized in C++ to specify the end boundary of the reverse iteration range, which is similar to the end function that does for forward iteration.
- It is a member function of the STL deque container, which is defined in the <deque> header file.
- We can use the rend function with the rbegin function to iterate via a deque in the reverse order.
- If we want to perform any task, it takes only (O(1)) time complexity.
Conclusion
In conclusion, the C++ deque rend is a member function of the deque container. The rend function is commonly utilized to return a reverse iterator thacpp tutorials to the theoretical element just before the first element of the deque, for the purpose of reverse traversal of the deque container. It is often used along with rbegin so that a programmer is able to iterate, search, or otherwise manipulate the elements of a deque from the back towards the front.
C++ Deque rend function FAQ's
1) What is the main purpose of the deque::rend function in C++?
The deque rend function is commonly utilized in C++ to return a reverse iterator to a position just before the first element in the deque. It is mainly utilized to indicate that a reverse iteration from the back of the deque to the front.
2) How is the rend function different than the end function in C++?
The deque end function is used in C++ to specify a position that is after the last element. In contrast, the deque rend function is commonly utilized to specify a position that is before the first element. Both end and rend are utilized to indicate the end of iterating on the respective side of the iterator.
3) Can we modify the deque elements using the rend function in C++?
No, we cannot modify the elements using the rend function because it doesn'cpp tutorial to a valid element in the deque.
4) What happens when we dereference the iterator event by the rend function in C++?
In C++, dereferencing the rend function will result in undefined behavior because icpp tutorials to a nonexistent theoretical element before the first element, which would have no definition in memory.
5) Is it better to use the rend function on a const deque in C++?
Yes, since the const deque rend function returns the constreverseiterator, any elements traversed using the reverse iterator cannot be modified.