DoubleEndedQueue.c

//11 a)

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

typedef struct Deque{
    int capacity;
    int*dq;
    int front;
    int rear;
}Deque;

void enqueue_front(Deque*p){
    if(p->rear==p->capacity-1){
        printf("Resizing...\n");
        int*newarr=(int*)realloc(p->dq,p->capacity*2*sizeof(int));
        if(newarr==NULL){
            printf("Memory allocation failed...\n");
            return;
        }
        p->dq=newarr;
        p->capacity*=2;
    }
    int val;
    printf("Enter the value to enqueue at front: ");
    scanf("%d",&val);
    if(p->front==-1){
        p->front=p->rear=0;
        p->dq[p->front]=val;
    }
    else if(p->front>0){
        p->dq[--p->front]=val;
    }
    else if(p->front==0){
        p->rear++;
        for(int i=p->rear;i>0;i--){
            p->dq[i]=p->dq[i-1];
        }
        p->dq[0]=val;
    }
}

void display(Deque*p){
    if(p->front==-1){
        printf("Queue Empty\n");
        return;
    }

    printf("Queue:\t");
    for(int i=p->front;i!=p->rear;i++){
        printf("%d ",p->dq[i]);
    }
    printf("%d\n",p->dq[p->rear]);
}

void enqueue_rear(Deque*p){
    if(p->rear==p->capacity-1){
        printf("Resizing...\n");
        int*newarr=(int*)realloc(p->dq,p->capacity*2*sizeof(int));
        if(newarr==NULL){
            printf("Memory allocation failed...\n");
            return;
        }
        p->dq=newarr;
        p->capacity*=2;
    }
    int val;
    printf("Enter the value to enqueue at rear: ");
    scanf("%d",&val);

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

void dequeue_front(Deque*p){
    if(p->front==-1){
        printf("Queue Underflow\n");
        return;
    }
    printf("Dequeued value: %d\n",p->dq[p->front]);

     if(p->front==p->rear){
        p->front=p->rear=-1;
        return;
    }

    for(int i=p->front;i<p->rear;i++){
        p->dq[i]=p->dq[i+1];
    }
    p->rear--;
}

void dequeue_rear(Deque*p){
    if(p->front==-1){
        printf("Queue Underflow\n");
        return;
    }
    printf("Dequeued value: %d\n",p->dq[p->rear]);
    if(p->rear==p->front){
        p->rear=p->front=-1;
        return;
    }
    p->rear--;
}

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

void main(){
    int ch;
    Deque*p=(Deque*)malloc(sizeof(Deque));
    if(p==NULL){
        printf("Memory Allocation Failed...\n");
        return;
    }
    p->front=p->rear=-1;
    printf("\nEnter the maximum capacity of the double ended queue: ");
    scanf("%d",&p->capacity);
    p->dq=(int*)calloc(p->capacity,sizeof(int));

    for(;;){
        printf("\nENTER:\n1. To insert at the front end\n2. To insert at the rear end\n3. To display\n4. To delete at the front end\n5. To delete at the rear end\n6. To peek\n0. To Exit\n");
        printf("Enter your choice from above: ");
        scanf("%d",&ch);

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

            case 2:
            enqueue_rear(p);
            break;

            case 3:
            display(p);
            break;

            case 4:
            dequeue_front(p);
            break;

            case 5:
            dequeue_rear(p);
            break;

            case 6:
            peek(p);
            break;

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

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