C++ Deque Pop Back Function

In the C++ programming language, the deque::popback method is a function shown by the deque (double-ended queue) class. The popback method is commonly utilized to remove the value of the object from the last element of the deque. It allows the insertion and removal of objects from either end of the deque in constant time, O(1). It enables us to manipulate the nested elements of a data structure effectively.

In C++ , the deque's popback function is commonly used to reduce the size of the object by one, but it does not return the type of the last deleted member. It can be used to delete the last element of a certain deque container. When we invoke the popfront function on an empty deque, it may produce undefined behavior. Therefore, it is also suitable to use the empty function to ensure that the deque is complete.

Syntax:

It has the following syntax:

deque_name.pop_back();

In this syntax,

Parameters:

• ✅ The pop_back function does not take any parameters.

Return Value:

• ✅ This function does not return any value (void return type).

C++ Simple deque pop_back function Example

Let us take an example to illustrate the deque pop_back function in C++.

Example

#include <iostream>

#include <deque>

using namespace std;    //using standard namespace

int main() {   //main function 

    // Creating a deque and initializing with some values

    deque<int> numbers = {5, 10, 15, 20, 25};

    cout << "Initial deque elements: ";

    for (int num : numbers)

        cout << num << " ";

    // using the pop_back() function to remove last element

    numbers.pop_back();

    cout << "\nAfter using pop_back(): ";

    for (int num : numbers)

        cout << num << " ";

    return 0;

}

Output:

Initial deque elements: 5 10 15 20 25

After using pop_back(): 5 10 15 20

Explanation:

In this example, we have created an integer deque named numbers that is initialized with five elements {5, 10, 15, 20, 25}. After that, we use the popback function to remove the last element (25) from the deque. Finally, the program prints the deque before and after using the popback function.

C++ Deque pop_back function Example Using Strings

Let us take an example to illustrate the deque pop_back function using strings in C++.

Example

#include <iostream>

#include <deque>

#include <string>

using namespace std;   //using standard namespace

int main() {   //main function

    // Create a deque of strings

    deque<string> fruits = {"Apple", "Banana", "Mango", "Orange"};

    cout << "Fruits in deque: ";

    for (const string &fruit : fruits)

        cout << fruit << " ";

    // using the pop_back() function to remove element

    fruits.pop_back();

    cout << "\nAfter removing the last fruit using pop_back(): ";

    for (const string &fruit : fruits)

        cout << fruit << " ";

    // Using the pop_back() function to remove one more element

    fruits.pop_back();

    cout << "\nAfter removing another fruit using pop_back(): ";

    for (const string &fruit : fruits)

        cout << fruit << " ";

    return 0;

}

Output:

Fruits in deque: Apple Banana Mango Orange

After removing the last fruit using pop_back(): Apple Banana Mango

After removing another fruit using pop_back(): Apple Banana

Explanation:

In this example, we have taken a string deque named fruits that is initialized with the "Apple," "Banana," "Mango," and "Orange". After that, we use the popback function to remove the "Orange" from the fruits deque. Next, we again call the popback function to remove the "Mango" element from the deque. Finally, "Apple" and "Banana" are the remaining elements in the deque.

Features of the deque pop_back function in C++

There are several features of the deque pop_back function in C++. Some of them are as follows:

• ✅ In C++, the deque pop_back function is commonly utilized to remove the elements that are present at the end of the deque container.
• ✅ When we call the deque pop_back function in the deque container, it always reduces the size of the deque by deleting one element from the container.
• ✅ This function allows us to modify the container by removing the last element from the deque container.
• ✅ The deque pop_back function does not throw any exceptions in a C++ program. However, if we call this function in the empty deque, it can lead to undefined behavior.
• ✅ When we perform any operation using the deque pop_back function in C++, it can take only constant time, i.e., O(1).

Conclusion:

In conclusion, the deque pop_back function in C++ provides a simple and effective method to remove the last element of a double-ended deque. The deque provides a flexible management of elements that allows us to add or remove elements from both the front and the back of the deque.

If we want to perform any operation using the deque's popback function in a C++ program, it can lead to undefined behavior. Overall, the popback is an easy method to safely and quickly remove or eliminate an element from the back of a C++ deque.

C++ deuque pop_back function FAQ's

1) What is the main purpose of the deque::pop_back function in C++?

The deque pop_back function in C++ programming is commonly utilized to reduce a deque container's size by one by removing the final element.

2) Is the deleted element returned by the pop_back function in C++?

No. The deleted value is not returned by the deque pop_back function. It is only utilized to remove the element.

3) What happens when we pass an empty deque to the pop_back function in C++?

In C++, when we call the pop_back function on an empty deque, it can produce undefined behavior or may cause a program crash.

4) How complex is the pop_back function in terms of time complexity in C++?

In C++, since the final element is eliminated in constant time by the deque pop_back function, its time complexity is O(1).

5) Does the pop_back function work with other C++ containers?

Yes. We can use the pop_back function with several other C++ containers, including vector, lists, and strings. It is commonly utilized to remove the last element from the container.