Queue Implementation using Array

Queue Implementation using Array

// C Program to Implement a Queue using an Array
#include <stdio.h>
#include <stdlib.h>

#define MAX 20

void insert();
void delete ();
void display();
int queue_array[MAX];
int rear = -1;
int front = -1;
int main()
{
	int choice;
	while (1)
	{
		printf("1.Insert element to queue \n");
		printf("2.Delete element from queue \n");
		printf("3.Display all elements of queue \n");
		printf("4.Quit \n");
		printf("Enter your choice : ");
		scanf("%d", &choice);
		switch (choice)
		{
		case 1:
			insert();
			break;
		case 2:
			delete ();
			break;
		case 3:
			display();
			break;
		case 4:
			exit(1);
		default:
			printf("Wrong choice \n");
		}
	}	 
}

void insert()
{
	int add_item;
	if (rear == MAX - 1)
		printf("Queue Overflow \n");
	else
	{
		if (front == -1)
			/*If queue is initially empty */
			front = 0;
		printf("Inset the element in queue : ");
		scanf("%d", &add_item);
		rear = rear + 1;
		queue_array[rear] = add_item;
	}
} /* End of insert() */

void delete ()
{
	if (front == -1 || front > rear)
	{
		printf("Queue Underflow \n");
		return;
	}
	else
	{
		printf("Element deleted from queue is : %d\n", queue_array[front]);
		front = front + 1;
	}
} /* End of delete() */

void display()
{
	int i;
	if (front == -1)
		printf("Queue is empty \n");
	else
	{
		printf("Queue is : \n");
		for (i = front; i <= rear; i++)
			printf("%d ", queue_array[i]);
		printf("\n");
	}
}

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