﻿ C++ Concatenate two queues

# C++ Queue Exercises: Concatenate two queues

## C++ Queue: Exercise-19 with Solution

Write a C++ program to concatenate two queues.

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
}

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;
}

// Function to concatenate two queues
void concatenate(Queue& q1, Queue& q2) {
while (!q2.isEmpty()) {
q1.enqueue(q2.peek()); // Enqueue elements from q2 into q1
q2.dequeue(); // Dequeue elements from q2
}
}
};

int main() {
cout << "Initialize a Queue." << endl;
Queue q1, q2, result_queue;
cout << "\nInsert some elements into the queue:" << endl;
q1.enqueue(1);
q1.enqueue(2);
q1.enqueue(3);
q1.enqueue(4);
cout << "Queue-1" << endl;
q1.display(); // Display elements of queue 1
q2.enqueue(5);
q2.enqueue(6);
q2.enqueue(1);
cout << "Queue-2" << endl;
q2.display(); // Display elements of queue 2
q1.concatenate(q1, q2); // Concatenate queue 1 and queue 2
cout << "\nConcatenate said two queues:" << endl;
q1.display(); // Display concatenated queue
return 0;
}
```
```

Sample Output:

```Initialize a Queue.

Insert some elements into the queue:
Queue-1
Queue elements are: 1 2 3 4
Queue-2
Queue elements are: 5 6 1

Concatenate said two queues:
Queue elements are: 1 2 3 4 5 6 1
```

Flowchart:

CPP Code Editor:

Previous C++ Exercise: Remove all elements greater than a number from a queue.
Next C++ Exercise: Copy one queue to another.

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