CircularQueue.c

//10 b)

#include <stdio.h>
#include <stdlib.h>

typedef struct Cirq{
    int front;
    int rear;
    int*q;
    int capacity;
}Cirq;

void enqueue(Cirq*p){
    if(p->front==((p->rear)+1)%p->capacity){
        printf("Resizing Circular Queue...\n");
        int*newarr=(int*)realloc(p->q,p->capacity*2*sizeof(int));
        if(newarr==NULL){
            printf("Memory allocation failed...\n");
            return;
        }
        p->q=newarr;
        if(p->front>p->rear){
            for(int i=0;i<=p->rear;i++){
                p->q[p->capacity+i]=p->q[i];
            }
            p->rear+=p->capacity;
        }
        p->capacity*=2;
    }

    int val;
    printf("Enter the value to enqueue: ");
    scanf("%d",&val);

    if(p->front==-1){
        p->front=0;
    }
    p->rear=(p->rear+1)%p->capacity;
    p->q[p->rear]=val;
}

void display(Cirq*p){
    if(p->front==-1){
        printf("Circular Queue is Empty\n");
        return;
    }
    
    printf("\nCircular Queue:\t");
    for(int i=p->front;i!=p->rear;i=(i+1)%p->capacity){
        printf("%d ",p->q[i]);
    }
    printf("%d\n",p->q[p->rear]);
}

void dequeue(Cirq*p){
    if(p->front==-1){
        printf("Circualr Queue Underflow\n");
        return;
    }
    printf("Dequeueud value: %d\n",p->q[p->front]);

    if(p->front==p->rear){
        p->front=p->rear=-1;
    }
    else{
        p->front=(p->front+1)%p->capacity;
    }
}

void peek(Cirq*p){
    if(p->front==-1){
        printf("Queue Empty\n");
        return;
    }
    printf("First element of Circular Queue: %d\n",p->q[p->front]);
}

void main(){
    int ch;
    Cirq*p=(Cirq*)malloc(sizeof(Cirq));
    if(p==NULL){
        printf("Memory allocation failed...\n");
        return;
    }
    p->front=p->rear=-1;
    printf("Enter maximum capacity of the circular queue: ");
    scanf("%d",&p->capacity);
    p->q=(int*)calloc(p->capacity,sizeof(int));

    for(;;){
    printf("\nENTER:\n1. To enqueue\n2. To display\n3. To dequeue\n4. To peek\n0. To EXIT\n");
    printf("Enter your choice from above: ");
    scanf("%d",&ch);

    switch(ch){
        case 1:
        enqueue(p);
        break;

        case 2:
        display(p);
        break;

        case 3:
        dequeue(p);
        break;

        case 4:
        peek(p);
        break;

        case 0:
        printf("Exiting...\n");
        free(p);
        free(p->q);
        exit(0);

        default:
        printf("Invalid Choice! Please Enter Again!\n");
    }
    }
}