Data-Structures-and-Algorithms/Queue.c at master · ashutoshkrris/Data-Structures-and-Algorithms · GitHub

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#include<stdio.h>
#include<stdlib.h>
#define max 100
int queue[max],n,x;
int front = -1;
int rear = -1;
void enqueue()
{
    if(rear==n-1)
    printf("Queue is full !!!");
    else if (front==-1 && rear==-1)
    {
        front=0;
        rear=0;
        printf("Enter the element : ");
        scanf("%d",&x);
        queue[rear]=x;
    }
    else
    {
        rear++;
        printf("Enter the element : ");
        scanf("%d",&x);
        queue[rear]=x;
    }
}
void dequeue()
{
    int item;
    if(front==-1 && rear==-1)
    printf("Queue is empty !!!");
    else if(front==rear)
    {
        item=queue[front];
        front==-1;
        rear==-1;
    }
    else
    {
        item=queue[front];
        front++;
    }
}
void peek()
{
    if(front==-1 && rear==-1)
    printf("Queue is empty !!!");
    else
    {
        printf("The front element is %d",queue[front]);
    }
}
void display()
{
    int i;
    if(front==-1 && rear==-1)
    printf("Queue is empty !!!");
    else
    {
        printf("Queue : ");
        for(i=front;i<=rear;i++)
        printf("%d ",queue[i]);
    }
}
int main()
{
    int op;
    printf("Enter the size of the queue : ");
    scanf("%d",&n);
    while(1)
    {
    printf("\n1. Insert an element\n2. Delete an element\n3. Peek\n4. Display the elements\n5. Exit\n\nEnter your choice : ");
    scanf("%d",&op);
    switch (op)
    {
    case 1 :
        enqueue();
        break;
    case 2 :
        dequeue();
        break;
    case 3 :
        peek();
        break;
    case 4 :
        display();
        break;
    case 5 :
        exit(0);

    default:
        printf("Wrong choice !!! Try again\n");
        break;
    }
    }
}