queue.c

#include <stdio.h>  
    
    # define max 10 
    int queue[max];  
    int front=-1;  
    int rear=-1; 

    void enqueue(int );
    void dequeue();
    void display_queue();

    int main()  
    {  
        int choice=1,x;   
        while(choice<4 && choice!=0)   
        {  
        printf("\n  1: Insert ");  
        printf("\n  2: Delete  ");  
        printf("\n  3: Display ");  
        printf("\nEnter your choice");  
        scanf("%d", &choice);  
        
        switch(choice)  
        {  
            
            case 1:  
        
            printf("Enter the element which is to be inserted");  
            scanf("%d", &x);  
            enqueue(x);  
            break;  
            case 2:  
            dequeue();  
            break;  
            case 3:  
            display_queue();  
    
        }}  
        return 0;  
    }  

    void enqueue(int element)  
    {  
        if(front==-1 && rear==-1)  
        {  
            front=0;  
            rear=0;  
            queue[rear]=element;  
        }  
        else if((rear+1)%max==front)  
        {  
            printf("Queue is overflow..");  
        }  
        else  
        {  
            rear=(rear+1)%max;       
            queue[rear]=element;       
        }  
    }  
    

    void  dequeue()  
    {  
        if((front==-1) && (rear==-1))  
        {  
            printf("\nQueue is underflow..");  
        }  
    else if(front==rear)  
    {  
    printf("\nThe dequeued element is %d", queue[front]);  
    front=-1;  
    rear=-1;  
    }   
    else  
    {  
        printf("\nThe dequeued element is %d", queue[front]);  
    front=(front+1)%max;  
    }  
    }  

    void display_queue()  
    {  
        int i=front;  
        if(front==-1 && rear==-1)  
        {  
            printf("\n Queue is empty..");  
        }  
        else  
        {  
            printf("\nElements in a Queue are :");  
            while(i<=rear)  
            {  
                printf("%d,", queue[i]);  
                i=(i+1)%max;  
            }  
        }  
    }