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

typedef struct node {
    int data;
    struct node *prev;
    struct node *next;
} Node;

Node *create_node(int data) {
    Node *new_node = (Node*)malloc(sizeof(Node));
    new_node->data = data;
    new_node->prev = NULL;
    new_node->next = NULL;
    return new_node;
}

void insert_node(Node **head, int data) {
    Node *new_node = create_node(data);
    if (*head == NULL) {
        *head = new_node;
        return;
    }
    Node *current = *head;
    while (current->next != NULL) {
        current = current->next;
    }
    current->next = new_node;
    new_node->prev = current;
}

void delete_node(Node **head, int data) {
    if (*head == NULL) {
        printf("List is empty!\n");
        return;
    }
    Node *current = *head;
    while (current != NULL) {
        if (current->data == data) {
            if (current->prev == NULL) { // delete head
                *head = current->next;
                if (*head != NULL) {
                    (*head)->prev = NULL;
                }
            } else if (current->next == NULL) { // delete tail
                current->prev->next = NULL;
            } else { // delete middle node
                current->prev->next = current->next;
                current->next->prev = current->prev;
            }
            free(current);
            printf("Node with data %d has been deleted.\n", data);
            return;
        }
        current = current->next;
    }
    printf("Node with data %d not found.\n", data);
}

void display_list(Node *head) {
    if (head == NULL) {
        printf("List is empty!\n");
        return;
    }
    printf("Doubly linked list:\n");
    while (head != NULL) {
        printf("%d ", head->data);
        head = head->next;
    }
    printf("\n");
}

int main() {
    Node *head = NULL;
    insert_node(&head, 5);
    insert_node(&head, 10);
    insert_node(&head, 15);
    insert_node(&head, 20);
    display_list(head);
    delete_node(&head, 10);
    display_list(head);
    delete_node(&head, 5);
    display_list(head);
    delete_node(&head, 20);
    display_list(head);
    delete_node(&head, 30);
    return 0;
}