C++ Deque

A deque, short for “double-ended queue,” is a data structure in C++ that allows for efficient insertion and deletion of elements from both ends. It combines the features of a stack and a queue, making it a versatile choice for various programming scenarios.

Creating a Deque in C++

To use a deque in C++, you need to include the <deque> header file. Here’s an example of how to create a deque:

#include <deque>
using namespace std;

int main() {
   deque<int> myDeque;
   // Perform operations on the deque
   return 0;
}

Inserting Elements into a Deque

Deque provides several methods for inserting elements:

1. push_front()

This function is used to insert an element at the front of the deque. Here’s an example:

myDeque.push_front(10);

2. push_back()

This function is used to insert an element at the back of the deque. Here’s an example:

myDeque.push_back(20);

Accessing Elements in a Deque

Deque allows you to access elements using various methods:

1. front()

This function returns the element at the front of the deque. Here’s an example:

int frontElement = myDeque.front();

2. back()

This function returns the element at the back of the deque. Here’s an example:

int backElement = myDeque.back();

Deleting Elements from a Deque

Deque provides methods for deleting elements:

1. pop_front()

This function removes the element at the front of the deque. Here’s an example:

myDeque.pop_front();

2. pop_back()

This function removes the element at the back of the deque. Here’s an example:

myDeque.pop_back();

Checking the Size of a Deque

To determine the number of elements in a deque, you can use the size() function. Here’s an example:

int dequeSize = myDeque.size();

Iterating Through a Deque

You can iterate through a deque using iterators or range-based for loops:

1. Using Iterators

Here’s an example of iterating through a deque using iterators:

deque<int>::iterator it;
for (it = myDeque.begin(); it != myDeque.end(); ++it) {
   cout << *it << " ";
}

2. Using Range-based For Loop

Here’s an example of iterating through a deque using a range-based for loop:

for (int element : myDeque) {
   cout << element << " ";
}

Example: Implementing a Deque

Let’s consider an example where we use a deque to implement a simple task manager:

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

void addTask(deque<string>& taskDeque, const string& task) {
   taskDeque.push_back(task);
}

void completeTask(deque<string>& taskDeque) {
   if (!taskDeque.empty()) {
      cout << "Completed task: " << taskDeque.front() << endl;
      taskDeque.pop_front();
   } else {
      cout << "No tasks to complete." << endl;
   }
}

int main() {
   deque<string> taskDeque;
   addTask(taskDeque, "Task 1");
   addTask(taskDeque, "Task 2");
   addTask(taskDeque, "Task 3");

   completeTask(taskDeque);
   completeTask(taskDeque);
   completeTask(taskDeque);
   completeTask(taskDeque);

   return 0;
}

In this example, the addTask() function adds tasks to the back of the deque, and the completeTask() function removes tasks from the front of the deque. The program outputs the completed tasks and handles the case when there are no tasks left to complete.

By using a deque, we can efficiently add and remove tasks from both ends, making it a suitable data structure for managing a task list.

That’s it! You now have a good understanding of C++ deque and how to use it in your programs. Deque provides a flexible way to handle data in a double-ended manner, making it a valuable tool in various programming scenarios.