﻿ C++ Find the maximum element of a queue

# 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: