﻿ C++ Mean, variance and standard deviation of all elements of a queue

# C++ Queue Exercises: Mean, variance and standard deviation of all elements of a queue

## C++ Queue: Exercise-8 with Solution

Write a C++ program to find the mean, variance and standard deviation of all elements 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;
}

float getMean() {
if (isEmpty()) {
cout << "Error: Queue is empty" << endl; // Display error message if the queue is empty
return 0;
}
float sum = 0;
for (int i = front; i <= rear; i++) {
sum += arr[i]; // Calculate sum of elements in the queue
}
return sum / (rear - front + 1); // Calculate and return the mean
}

float getVariance() {
if (isEmpty()) {
cout << "Error: Queue is empty" << endl; // Display error message if the queue is empty
return 0;
}
float mean = getMean();
float variance = 0;
for (int i = front; i <= rear; i++) {
variance += pow(arr[i] - mean, 2); // Calculate sum of squared differences from mean
}
return variance / (rear - front + 1); // Calculate and return the variance
}

float getStdDev() {
return sqrt(getVariance()); // Calculate and return the standard deviation using variance
}
};

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();

// Calculate and display mean, variance, and standard deviation of queue elements
cout << "Mean: " << q.getMean() << endl;
cout << "Variance: " << q.getVariance() << endl;
cout << "Standard Deviation: " << q.getStdDev() << endl;

cout << "\nRemove two elements from the said queue: " << q.getStdDev() << endl;
q.dequeue();
q.dequeue();
q.display();

// Calculate and display mean, variance, and standard deviation after removing elements
cout << "Mean: " << q.getMean() << endl;
cout << "Variance: " << q.getVariance() << endl;
cout << "Standard Deviation: " << q.getStdDev() << endl;

return 0;
}
```
```

Sample Output:

```Initialize a Queue.

Insert some elements into the queue:
Queue elements are: 1 2 3 4 5
Mean: 3
Variance: 2
Standard Deviation: 1.41421

Remove two elements from the said queue: 1.41421
Queue elements are: 3 4 5
Mean: 4
Variance: 0.666667
Standard Deviation: 0.816497
```

Flowchart:

CPP Code Editor:

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Previous C++ Exercise: Find the mode of all elements of a queue.
Next C++ Exercise: Find the maximum element of a queue.

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