queue.cpp

#include <bits/stdc++.h> 
using namespace std; 

struct Queue { 
	int front, rear, capacity; 
	int* queue; 
	Queue(int c) 
	{ 
		front = rear = 0; 
		capacity = c; 
		queue = new int; 
	} 

	// function to insert an element 
	// at the rear of the queue 
	void queueEnqueue(int data) 
	{ 
		// check queue is full or not 
		if (capacity == rear) { 
			printf("\nQueue is full\n"); 
			return; 
		} 

		// insert element at the rear 
		else { 
			queue[rear] = data; 
			rear++; 
		} 
		return; 
	} 

	// function to delete an element 
	// from the front of the queue 
	void queueDequeue() 
	{ 
		// if queue is empty 
		if (front == rear) { 
			printf("\nQueue is empty\n"); 
			return; 
		} 

		// shift all the elements from index 2 till rear 
		// to the left by one 
		else { 
			for (int i = 0; i < rear - 1; i++) { 
				queue[i] = queue[i + 1]; 
			} 

			// decrement rear 
			rear--; 
		} 
		return; 
	} 

	// print queue elements 
	void queueDisplay() 
	{ 
		int i; 
		if (front == rear) { 
			printf("\nQueue is Empty\n"); 
			return; 
		} 

		// traverse front to rear and print elements 
		for (i = front; i < rear; i++) { 
			printf(" %d <-- ", queue[i]); 
		} 
		return; 
	} 

	// print front of queue 
	void queueFront() 
	{ 
		if (front == rear) { 
			printf("\nQueue is Empty\n"); 
			return; 
		} 
		printf("\nFront Element is: %d", queue[front]); 
		return; 
	} 
}; 

// Driver code 
int main(void) 
{ 
	// Create a queue of capacity 4 
	Queue q(4); 

	// inserting elements in the queue 
	q.queueEnqueue(1); 
	q.queueEnqueue(2); 
	q.queueEnqueue(3); 
	q.queueEnqueue(4); 

	// print Queue elements 
	q.queueDisplay(); 

	// insert element in the queue 
	q.queueEnqueue(5); 

  // delete element from front of queue
	q.queueDequeue(); 
	
  // print front of the queue 
	q.queueFront(); 

	return 0; 
}