C++ Queue Exercises: Find the maximum element of a queue

C++ Queue: Exercise-9 with Solution

Write a C++ program to find the maximum element of 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; // Front index of the queue
    int rear; // Rear index of the queue
    int arr[MAX_SIZE]; // Array to store elements

  public:
    Queue() {
      front = -1; // Initialize front index to -1
      rear = -1; // Initialize 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 message if the queue is full
        return;
      }
      if (isEmpty()) {
        front = 0;
        rear = 0;
      } else {
        rear++;
      }
      arr[rear] = x; // Insert the element at the rear index
    }

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

    void display() {
      if (isEmpty()) {
        cout << "Error: Queue is empty" << endl; // Display error message 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 findMax(Queue q) {
      int max = q.peek(); // Initialize max with the first element of the queue
      while (!q.isEmpty()) {
        int curr = q.peek(); // Get the current element
        if (curr > max) {
          max = curr; // Update max if the current element is greater
        }
        q.dequeue(); // Remove the element from the queue
      }
      return max; // Return the maximum element
    }
};

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.display();
  int max = q.findMax(q); // Find the maximum element in the queue
  cout << "Maximum element of the said queue: " << max << endl;
  cout << "\nInsert two more elements into the queue:" << endl;
  q.enqueue(-6);
  q.enqueue(7);
  q.display();
  max = q.findMax(q); // Find the maximum element again after inserting new elements
  cout << "Maximum element of the said queue: " << max << endl;
  return 0;
}

Sample Output:

Initialize a Queue.

Insert some elements into the queue:
Queue elements are: 1 2 3 4 5 
Maximum element of the said queue: 5

Insert two more elements into the queue:
Queue elements are: 1 2 3 4 5 -6 7 
Maximum element of the said queue: 7

Flowchart:

CPP Code Editor:

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Previous C++ Exercise: Mean, variance and standard deviation of all elements of a queue.
Next C++ Exercise: Find the minimum element of a queue.