w3resource

C++ Queue Exercises: Remove all the elements from a queue

C++ Queue: Exercise-14 with Solution

Write a C++ program to remove all the elements from a queue.

Sample Solution:

C Code:

#include <iostream>
#include <map>
#include <cmath>

using namespace std;

const int MAX_SIZE = 100;

class Queue {
  private:
    int front; // Holds the front index of the queue
    int rear; // Holds the rear index of the queue
    int arr[MAX_SIZE]; // Array to hold queue elements

  public:
    Queue() {
      front = -1; // Initialize front index to -1
      rear = -1; // Initialize rear index to -1
    }

    bool isFull() {
      return (rear == MAX_SIZE - 1); // Checks if the queue is full
    }

    bool isEmpty() {
      return (front == -1 && rear == -1); // Checks if the queue is empty
    }

    void enqueue(int x) {
      if (isFull()) {
        cout << "Error: Queue is full" << endl; // Displays error if the queue is full
        return;
      }
      if (isEmpty()) {
        front = 0;
        rear = 0;
      } else {
        rear++;
      }
      arr[rear] = x; // Adds an element to the rear of the queue
    }

    void dequeue() {
      if (isEmpty()) {
        cout << "Error: Queue is empty" << endl; // Displays error if the queue is empty
        return;
      }
      if (front == rear) {
        front = -1;
        rear = -1;
      } else {
        front++;
      }
    }

    int peek() {
      if (isEmpty()) {
        cout << "Error: Queue is empty" << endl; // Displays error if the queue is empty
        return -1;
      }
      return arr[front]; // Returns the element at the front of the queue
    }

    void display() {
      if (isEmpty()) {
        cout << "Error: Queue is empty" << endl; // Displays error if the queue is empty
        return;
      }
      cout << "Queue elements are: ";
      for (int i = front; i <= rear; i++) {
        cout << arr[i] << " "; // Displays all elements in the queue
      }
      cout << endl;
    }

    void clear() {
      while (!isEmpty()) {
        dequeue(); // Removes all elements from the queue
      }
    }

};

int main() {
  cout << "Initialize a Queue." << endl;
  Queue q;
  cout << "\nInsert some elements into the queue:" << endl;
  q.enqueue(1);
  q.enqueue(2);
  q.enqueue(3);
  q.enqueue(4);
  q.enqueue(5);
  q.enqueue(6);
  q.display();
  cout << "\nRemove all the elements from the said queue:" << endl;
  q.clear();
  q.display(); // Display an empty queue
  cout << "\nInput two more elements into the queue:" << endl;
  q.enqueue(1);
  q.enqueue(2);
  q.display();
  cout << "\nRemove all the elements from the said queue:" << endl;
  q.clear();
  q.display(); // Display an empty queue again
  return 0;
}

Sample Output:

Initialize a Queue.

Insert some elements into the queue:
Queue elements are: 1 2 3 4 5 6 

Remove all the elements from the said queue:
Error: Queue is empty

Input two more elements into the queue:
Queue elements are: 1 2 

Remove all the elements from the said queue:
Error: Queue is empty

Flowchart:

Flowchart: Remove all the elements from a queue .
Flowchart: Remove all the elements from a queue .
Flowchart: Remove all the elements from a queue .

CPP Code Editor:

Contribute your code and comments through Disqus.

Previous C++ Exercise: Remove a given element from a queue.
Next C++ Exercise: Remove all even elements from a queue.

What is the difficulty level of this exercise?



Become a Patron!

Follow us on Facebook and Twitter for latest update.

It will be nice if you may share this link in any developer community or anywhere else, from where other developers may find this content. Thanks.

https://www.w3resource.com/cpp-exercises/queue/cpp-queue-exercise-14.php