STL-deque in C++ Programming

Deque is a shorthand for doubly ended queue. Deque allows fast insertion and deletion at both ends of the queue.

This program demonstrates the use of deque (double-ended queue) container in C++ STL.

First, the deque container is declared and initialized with a single element 10 using the initializer list syntax.

Then, three more elements are added to the deque using push_back() and push_front() functions. The elements are printed using a range-based for loop.

The program also demonstrates the usage of some common member functions of the deque container:

size(): returns the number of elements in the deque.
empty(): returns true if the deque is empty, false otherwise.
at(): returns the element at the specified index. If the index is out of range, an exception is thrown.
front(): returns the first element of the deque.
back(): returns the last element of the deque.
pop_back(): removes the last element of the deque.
pop_front(): removes the first element of the deque.

Finally, the deque is printed again using a range-based for loop after removing the first and last elements.

Source Code

#include<iostream>
#include<deque>
using namespace std;
//STL-Deque in C++
int main()
{
    deque<int> d={10};
    d.push_back(25);
    d.push_front(45);
    for(int x : d){
	cout<<" "<<x;
    }
    cout<<endl;
    cout<<"Deque Size : "<<d.size()<<endl;
    cout<<"Deque Empty or Not : "<<d.empty()<<endl;
    cout<<"Deque Element At 2 Index : "<<d.at(2)<<endl;
    cout<<"Deque First Element: "<<d.front()<<endl;
    cout<<"Deque Last Element: "<<d.back()<<endl;
    d.pop_back();
    d.pop_front();
    for(int x : d){
	cout<<" "<<x;
    }
    return 0;
}

Output

 45 10 25
Deque Size : 3
Deque Empty or Not : 0
Deque Element At 2 Index : 25
Deque First Element: 45
Deque Last Element: 25
 10

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