Introduction to Queues

Queues are another fundamental data structure that follows the FIFO (First-In-First-Out) principle. In a queue, the element that is added first is the first one to be removed. Just like waiting in a line, where the first person to join the line is the first one to be served.

Queues have a wide range of applications in computer science and real-world scenarios. Let's explore some of the common use cases of queues:

1. Job Scheduling: In operating systems, queues are used to schedule different tasks or jobs. Each process is added to a queue and then executed based on its priority or arrival time.
2. Breadth-First Search (BFS): Queues are used in graph algorithms like BFS to traverse the nodes level by level. The nodes are explored in the order they were added to the queue.
3. Printers: Printers often use queues to manage print requests. Each print request is added to the queue and processed in the order of arrival.

Let's take a look at a simple C++ implementation of a queue:

1#include <iostream>
2#include <queue>
3using namespace std;
4
5int main() {
6  queue<int> q;
7
8  // Enqueue elements
9  q.push(10);
10  q.push(20);
11  q.push(30);
12
13  // Print front element
14  cout << "Front element: " << q.front() << endl;
15
16  // Dequeue elements
17  q.pop();
18  q.pop();
19
20  // Print front element
21  cout << "Front element: " << q.front() << endl;
22
23  return 0;
24}

In the code above, we include the <queue> header file to use the queue data structure in C++. We create a queue object q and perform operations like push to enqueue elements and pop to dequeue elements. The front function is used to retrieve the front element of the queue.

Queues are essential in many algorithms and provide an efficient way to manage and process data. In the upcoming lessons, we will dive deeper into queue operations and different implementations.

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#include <iostream>

using namespace std;

​

int main() {

  // Queue implementation goes here

  return 0;

}