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// Online C compiler to run C program online
#include <stdio.h>
#include <stdlib.h>
struct node{
    int data;
    struct node *next;
    struct node *prev;
}*start=NULL,*last=NULL;
void createdll(int data){
    struct node *ptr=(struct node*)malloc(sizeof(struct node));
    ptr->data=data;
    ptr->next=NULL;
    ptr->prev=NULL;
    
    if(start==NULL){
        start=ptr;
        last=ptr;
    }
    else{
        ptr->prev=last;
        last->next=ptr;
        last=ptr;
    }
}

void print(struct node *start){
    struct node *temp=start;
    while(temp!=NULL){
        printf("%d",temp->data);
        temp=temp->next;
    }
}
void deletefirst(){
    struct node *temp=start;
    start=start->next;
    free(temp);
}

void addfirst(struct node *start,int data){
     struct node *ptr=(struct node*)malloc(sizeof(struct node));
    ptr->data=data;
    ptr->next=start->next;
    ptr->prev=NULL;
    start->next->prev=ptr;
    start=ptr;
    
}
void add_after(struct node* start, int n , int given)
{
    struct node* t = start;

    struct node* ptr = (struct node*) malloc(sizeof(struct node));
    ptr->data = n;
    ptr->next = NULL;
    ptr->prev = NULL;

    while(t->data != given){
        t = t->next;
   } 
    ptr->next = t->next;
    ptr->prev = t;

    t->next->prev = ptr;
    t->next = ptr;    
}
void add_before(struct node* start, int n, int given)
{
    struct node* ptr = (struct node*) malloc(sizeof(struct node));
    ptr->data = n;
    ptr->next = NULL;
    ptr->prev = NULL;

    struct node* temp = start;
    while(temp->data != given)
    {
        temp = temp->next;
    }

    ptr->next = temp;
    ptr->prev = temp->prev;
    temp->prev->next = ptr;
    temp->prev = ptr;
}
void delete_after(struct no* start, int given)
{
struct node *temp = start;
    while (temp != NULL && temp->data != given)
    {
        temp = temp->next;
    }
    struct node* t = temp->next;
    temp->next = temp->next->next;
    free(t);    
}
void reverse(struct node *start){
	struct node *t1=start,*t2=last;
	while(t2->next!=t1 && t1!=t2){
		int temp=t1->data;
		t1->data=t2->data;
		t2->data=temp;
		t1=t1->next;
		t2=t2->prev;
	}
}

void main() {
    int n;
    printf("enter no. of nodes=");
    scanf("%d",&n);
    for(int i=0;i<n;i++){
        int data;
        scanf("%d",&data);
        createdll(data);
    }
    print(start);
    deletefirst();
     print(start);
    addfirst(start,13);
    print(start);
    add_before(start,1221,23);
    add_after(start,1221,23);
}