doublecircular

#include<stdio.h>
#include<stdlib.h>
struct node{
	struct node *prev,*next;
	int data;
};
struct node *head=NULL,*new_node,*ptr,*preptr,*temp,*del;
struct node *createnode(int item){
	new_node=(struct node*)malloc(sizeof(struct node));
	new_node->data=item;
	return new_node;
}
void display(){
	if(head==NULL){
		printf("Empty list");
		return;
	}
	temp=head;
	while(temp->next!=head){
		printf("%d->",temp->data);
		temp=temp->next;
	}
	printf("%d",temp->data);
}
void insert_beg(int item){
	new_node=createnode(item);
	if(head==NULL){
		head=new_node;
		new_node->prev=new_node;
		new_node->next=head;
	}
	else{
		new_node->next=head;
		head->prev->next=new_node;
		new_node->prev=head->prev;
		head->prev=new_node;
		head=new_node;
	}
	printf("The new list after insertion is: ");
	display();
}
void insert_end(int item){
	new_node=createnode(item);
	if(head==NULL){
		head=new_node;
		new_node->prev=new_node;
		new_node->next=head;
	}
	else{	
		head->prev->next=new_node;
		new_node->next=head;
		head->prev=new_node;
	printf("The new list after insertion is: ");
	display();
}
}
void insert_before(int val, int item){
    new_node = createnode(item);
    if(head == NULL){
        printf("Empty list");
        return;
    }
    ptr = head;
    if(head->data == val){
        insert_beg(item);
        return;
    }
    do{
        ptr = ptr->next;
    } while(ptr != head && ptr->data != val);
    if(ptr == head){
        printf("Node doesn't exist");
        return;
    }
    new_node->next = ptr;
    new_node->prev = ptr->prev;
    ptr->prev->next = new_node;
    ptr->prev = new_node;
    printf("The new list after insertion is: ");
    display();
}
void insert_after(int val, int item){
    new_node = createnode(item);
    if(head == NULL){
        printf("Empty list");
        return;
    }
    ptr = head;
    do{
        ptr = ptr->next;
    } while(ptr != head && ptr->data != val);
    if(ptr == head){
        printf("Node doesn't exist");
        return;
    }
    new_node->prev = ptr;
    new_node->next = ptr->next;
    ptr->next = new_node;
    printf("The new list after insertion is: ");
    display();
}
void delete_beg(){
	if(head==NULL){
		printf("Empty list");
		return;
	}
	if (head->next == head) {
		free(head);
        head = NULL;
    } 
    else{
	(head->prev)->next=head->next;
	(head->next)->prev=head->prev;
	del=head;
	head=head->next;
	free(del);
	printf("The new list after deletion is: ");
}
	display();
}
void delete_last() {
    if (head == NULL) {
        printf("Empty list");
        return;
    }

    if (head->next == head) {
        free(head);
        head = NULL;
    } else {
        temp = head->prev;  
        head->prev = temp->prev;        
        temp->prev->next = head;        
        free(temp);                     
    }

    printf("The new list after deletion is: ");
    display();  
}
void delete_node(int val){
	if(head==NULL){
		printf("Empty list");
		return;
	}
	ptr=head;
	if(ptr->data==val){
		delete_beg();
		return;
	}
		while(ptr->data!=val){
			ptr=ptr->next;
			if(ptr==head){
				printf("Node doesn't exist");
				return;
			}
		}
		ptr->prev->next=ptr->next;
		ptr->next->prev=ptr->prev;
		free(ptr);
	printf("The new list after deletion is: ");
	display();
}
void delete_before(int item) {
    if (head == NULL) {
        printf("Empty list\n");
        return;
    }

    ptr = head;
    preptr = head->prev;

    // Find the node containing 'item'
    while (ptr->next != head && ptr->next->data != item) {
        preptr = ptr;
        ptr = ptr->next;
    }

    // Check if the node with 'item' was found
    if (ptr->next == head || ptr->next->data != item) {
        printf("Item not found in the list.\n");
        return;
    }

    // Check if 'ptr' is the first or second node
    if (ptr == head || ptr->next == head) {
        printf("No node before the second node.\n");
        return;
    }

    // Update pointers to delete the node before 'item'
    preptr->prev->next = ptr;
    ptr->prev = preptr->prev;
    free(preptr);
    printf("The new list after deletion is: ");
    display();
}

void delete_after(int item) {
    if (head == NULL) {
        printf("List is empty, nothing to delete.\n");
        return;
    }
    ptr = head;
    preptr = ptr;
    if (ptr->data == item) {
        while (preptr->next != head) {
            preptr = preptr->next;
        }
        preptr->next = ptr->next;
        ptr->next->prev = preptr;
        if (ptr == head) {
            head = preptr->next;
        }
        if (head == ptr) {
            head = NULL;
        }

        free(ptr);
        display();
        return;
    }
    while (ptr->data != item && ptr->next != head) {
        preptr = ptr;
        ptr = ptr->next;
    }
    if (ptr->data != item) {
        printf("Item not found in the list.\n");
        return;
    }
    preptr = ptr->prev;
    preptr->next = ptr->next;
    ptr->next->prev = preptr;
    free(ptr);
    display();
}
int main(){
    int option, item, val;
    do {
        printf("\n\n*****MAIN MENU*****");
        printf("\n 1: Display list");
        printf("\n 2: Insert a node at the beginning");
        printf("\n 3: Insert a node at the end");
        printf("\n 4: Add a node before a given node");
        printf("\n 5: Add a node after a given node");
        printf("\n 6: Delete a node from the beginning");
        printf("\n 7: Delete a node at the end");
        printf("\n 8: Delete a given node");
        printf("\n 9: Delete before a given node");
        printf("\n 10: Delete after a given node");
        printf("\n 11: Exit");
        printf("\n Enter your option: ");
        scanf("%d", &option);
        switch(option) {
            case 1:
                display();
                break;
            case 2:
                printf("Enter the item to be inserted: ");
                scanf("%d", &item);
                insert_beg(item);
                break;
            case 3:
                printf("Enter the item to be inserted: ");
                scanf("%d", &item);
                insert_end(item);
                break;
            case 4:
                printf("Enter the item: ");
                scanf("%d", &item);
                printf("Enter the value before which you want to insert: ");
                scanf("%d", &val);
                insert_before(val, item);
                break;
            case 5:
                printf("Enter the item to be inserted: ");
                scanf("%d", &item);
                printf("Enter the value after which you want to insert: ");
                scanf("%d", &val);
                insert_after(val, item);
                break;
            case 6:
                delete_beg();
                break;
            case 7:
                delete_last();
                break;
            case 8:
                printf("Enter the item to be deleted: ");
                scanf("%d", &item);
                delete_node(item);
                break;
            case 9:
                printf("Enter the value before which you want to delete: ");
                scanf("%d", &val);
                delete_before(val);
                break;
            case 10:
                printf("Enter the value after which you want to delete: ");
                scanf("%d", &val);
                delete_after(val);
                break;
        }
    } while(option != 11);
    return 0;
}