﻿ C++ Intersection of two queues

# C++ Queue Exercises: Intersection of two queues

## C++ Queue: Exercise-26 with Solution

Write a C++ program to find the intersection of 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
}

Queue findIntersection(Queue q1, Queue q2) {
Queue q3; // Initialize an empty queue to store the intersection
while (!q1.isEmpty()) {
int x = q1.peek(); // Get the element at the front of q1
q1.dequeue(); // Remove the element from q1
Queue temp = q2; // Create a temporary queue for q2
while (!temp.isEmpty()) {
int y = temp.peek(); // Get the element at the front of the temporary queue
temp.dequeue(); // Remove the element from the temporary queue
if (x == y) {
q3.enqueue(x); // If x is equal to y, enqueue x to q3
break;
}
}
}
return q3; // Return the intersection 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;
}
};

int main() {
cout << "Initialize three Queues." << endl;
Queue q1, q2, q3; // Creating instances of Queue
q1.enqueue(1);
q1.enqueue(2);
q1.enqueue(3);
q2.enqueue(1);
q2.enqueue(2);
q2.enqueue(4);
q3.enqueue(3);
q3.enqueue(2);
q3.enqueue(1);
cout << "Queue-1" << endl;
q1.display(); // Display elements of Queue-1
cout << "Queue-2" << endl;
q2.display(); // Display elements of Queue-2
cout << "Queue-3" << endl;
q3.display(); // Display elements of Queue-3
cout << "\nIntersection of two queues q1 and q2:" << endl;
Queue result = q1.findIntersection(q1, q2); // Get intersection of q1 and q2
result.display(); // Display the intersection
cout << "\nIntersection of two queues q2 and q3:" << endl;
Queue result1 = q1.findIntersection(q2, q3); // Get intersection of q2 and q3
result1.display(); // Display the intersection
cout << "\nIntersection of two queues q3 and q1:" << endl;
Queue result2 = q1.findIntersection(q3, q1); // Get intersection of q3 and q1
result2.display(); // Display the intersection
return 0;
}
```
```

Sample Output:

```Initialize three Queues.
Queue-1
Queue elements are: 1 2 3
Queue-2
Queue elements are: 1 2 4
Queue-3
Queue elements are: 3 2 1

Intersection of two queues q1 and q2:
Queue elements are: 1 2

Intersection of two queues q2 and q3:
Queue elements are: 1 2

Intersection of two queues q3 and q1:
Queue elements are: 3 2 1
```

Flowchart:

CPP Code Editor: