C++ Queue Exercises: Find the top and bottom elements of a queue

C++ Queue: Exercise-21 with Solution

Write a C++ program to find the top and bottom elements of a queue.

Sample Solution:

C Code:

 #include <iostream> // Including necessary library for input and output operations

using namespace std;

const int MAX_SIZE = 100; // Maximum size for the queue

class Queue {
private:
    int front; // Front of the queue
    int rear; // Rear of the queue
    int arr[MAX_SIZE]; // Array to store queue elements

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

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

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

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

    void dequeue() {
        if (isEmpty()) {
            cout << "Error: Queue is empty" << endl; // Display 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; // Display error if the queue is empty
            return -1;
        }
        return arr[front]; // Return the element at the front of the queue
    }

    // Function to get the top element of the queue
    int getTop() {
        return peek();
    }

    // Function to get the bottom element of the queue
    int bottom() {
        if (isEmpty()) {
            cout << "Error: Queue is empty" << endl; // Display error if the queue is empty
            return -1;
        }
        return arr[rear]; // Return the element at the rear of the queue
    }

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

int main() {
    cout << "Initialize a Queue." << endl;
    Queue q1; // Creating an instance of Queue
    cout << "\nInsert some elements into the queue:" << endl;
    q1.enqueue(1);
    q1.enqueue(2);
    q1.enqueue(3);
    q1.enqueue(4);
    q1.enqueue(5);
    q1.enqueue(6);
    q1.display(); // Display elements of the queue
    cout << "\nTop element of the Queue is: " << q1.getTop() << endl; // Get the top element of the queue
    cout << "Bottom element of the Queue is: " << q1.bottom() << endl; // Get the bottom element of the queue
    cout << "\nRemove two elements from the above Queue:" << endl;
    q1.dequeue();
    q1.dequeue();
    q1.display(); // Display elements of the queue after dequeuing
    cout << "\nTop element of the Queue is: " << q1.getTop() << endl; // Get the top element of the updated queue
    cout << "Bottom element of the Queue is: " << q1.bottom() << endl; // Get the bottom element of the updated queue
    return 0;
}

Sample Output:

Initialize a Queue.

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

Top element of the Queue is: 1
Botttom element of the Queue is: 6

Remove two elements from the above Queue:
Queue elements are: 3 4 5 6 

Top element of the Queue is: 3
Botttom element of the Queue is: 6

Flowchart:

CPP Code Editor:

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