﻿ C++ Find the second highest element of a queue

# C++ Queue Exercises: Find the second highest element of a queue

## C++ Queue: Exercise-11 with Solution

Write a C++ program to find the second highest 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; // Stores the front index of the queue
int rear; // Stores 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;
}

int second_Highest(Queue q) {
int max1 = -1; // Initialize the first maximum element
int max2 = -1; // Initialize the second maximum element
while (!q.isEmpty()) {
int val = q.peek();
q.dequeue();
if (val > max1) {
max2 = max1;
max1 = val;
} else if (val > max2) {
max2 = val;
}
}
return max2; // Return the second highest element in 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.display();
int sh_el = q.second_Highest(q); // Find the second highest element in the queue
cout << "Second highest element of the said queue: " << sh_el << endl;
cout << "\nInsert two more elements into the queue:" << endl;
q.enqueue(6);
q.enqueue(7);
q.display();
sh_el = q.second_Highest(q); // Find the second highest element again after inserting new elements
cout << "Second highest element of the said queue: " << sh_el << endl;
return 0;
}
```
```

Sample Output:

```Initialize a Queue.

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

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

Flowchart:

CPP Code Editor: