C++ Queue Exercises: Check if two queues are equal

C++ Queue: Exercise-25 with Solution

Write a C++ program to check if two queues are equal.

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
    }

    bool isEqual(Queue q1, Queue q2) {
        if (q1.isEmpty() && q2.isEmpty()) {
            return true; // Return true if both queues are empty
        }
        if (q1.isEmpty() || q2.isEmpty()) {
            return false; // Return false if only one of the queues is empty
        }
        if (q1.peek() != q2.peek()) {
            return false; // Return false if the front elements of the queues are not equal
        }
        Queue temp1 = q1;
        Queue temp2 = q2;
        while (!temp1.isEmpty() && !temp2.isEmpty()) {
            if (temp1.peek() != temp2.peek()) {
                return false; // Return false if any corresponding elements of queues are not equal
            }
            temp1.dequeue();
            temp2.dequeue();
        }
        return (temp1.isEmpty() && temp2.isEmpty()); // Return true if both queues are empty after comparisons
    }

    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;
    }
};

int main() {
    cout << "Initialize three Queues." << endl;
    Queue q1, q2, q3; // Creating instances of Queue
    q1.enqueue(1);
    q1.enqueue(2);
    q1.enqueue(3);
    q2.enqueue(1);
    q2.enqueue(2);
    q2.enqueue(3);
    q3.enqueue(3);
    q3.enqueue(2);
    q3.enqueue(1);
    cout << "Queue-1" << endl;
    q1.display(); // Display elements of Queue-1
    cout << "Queue-2" << endl;
    q2.display(); // Display elements of Queue-2
    cout << "Queue-3" << endl;
    q3.display(); // Display elements of Queue-3
    cout << "\nCheck if Queue-1 and Queue-2 are equal? " << q1.isEqual(q1, q2) << endl;
    cout << "\nCheck if Queue-2 and Queue-3 are equal? " << q1.isEqual(q2, q3) << endl;
    cout << "\nCheck if Queue-1 and Queue-3 are equal? " << q1.isEqual(q1, q3) << endl;
    return 0;
}

Sample Output:

Initialize three Queues.
Queue-1
Queue elements are: 1 2 3 
Queue-2
Queue elements are: 1 2 3 
Queue-3
Queue elements are: 3 2 1 

Cheque Queue-1 and Queue-2 are equal? 1

Cheque Queue-2 and Queue-3 are equal? 0

Cheque Queue-1 and Queue-3 are equal? 0

Flowchart:

CPP Code Editor:

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Previous C++ Exercise: Find the position of an element in a queue.
Next C++ Exercise: Intersection of two queues.