//Write a menu driven program to perform the following on a doubly linked list
//DS LAB MANUAL
// i.) Insert an element at the rear end of the list
// ii.) Delete an element from the rear end of the list
// iii.) Insert an element at a given position of the list
// iv.) Delete an element from a given position of the list
// v.) Insert an element after another element
// vi.) Insert an element before another element
// vii.) Traverse the list
// viii.) Reverse the list

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

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

struct Node* head = NULL;

void insertRear(int data) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;
    newNode->next = NULL;

    if (head == NULL) {
        newNode->prev = NULL;
        head = newNode;
        return;
    }

    struct Node* temp = head;
    while (temp->next != NULL)
        temp = temp->next;

    temp->next = newNode;
    newNode->prev = temp;
}

void deleteRear() {
    if (head == NULL) {
        printf("List is empty\n");
        return;
    }

    if (head->next == NULL) {
        free(head);
        head = NULL;
        return;
    }

    struct Node* temp = head;
    while (temp->next != NULL)
        temp = temp->next;

    temp->prev->next = NULL;
    free(temp);
}

void insertPosition(int data, int position) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;

    if (position == 1) {
        newNode->prev = NULL;
        newNode->next = head;
        if (head != NULL)
            head->prev = newNode;
        head = newNode;
        return;
    }

    struct Node* temp = head;
    for (int i = 1; i < position - 1 && temp != NULL; i++)
        temp = temp->next;

    if (temp == NULL) {
        printf("Position out of range\n");
        return;
    }

    newNode->next = temp->next;
    newNode->prev = temp;
    if (temp->next != NULL)
        temp->next->prev = newNode;
    temp->next = newNode;
}

void deletePosition(int position) {
    if (head == NULL) {
        printf("List is empty\n");
        return;
    }

    struct Node* temp = head;

    if (position == 1) {
        head = head->next;
        if (head != NULL)
            head->prev = NULL;
        free(temp);
        return;
    }

    for (int i = 1; i < position && temp != NULL; i++)
        temp = temp->next;

    if (temp == NULL) {
        printf("Position out of range\n");
        return;
    }

    temp->prev->next = temp->next;
    if (temp->next != NULL)
        temp->next->prev = temp->prev;
    free(temp);
}

void insertAfter(int data, int key) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;

    struct Node* temp = head;
    while (temp != NULL && temp->data != key)
        temp = temp->next;

    if (temp == NULL) {
        printf("Key not found\n");
        return;
    }

    newNode->next = temp->next;
    newNode->prev = temp;
    if (temp->next != NULL)
        temp->next->prev = newNode;
    temp->next = newNode;
}

void insertBefore(int data, int key) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;

    if (head == NULL) {
        printf("List is empty\n");
        return;
    }

    if (head->data == key) {
        newNode->next = head;
        newNode->prev = NULL;
        head->prev = newNode;
        head = newNode;
        return;
    }

    struct Node* temp = head;
    while (temp->next != NULL && temp->next->data != key)
        temp = temp->next;

    if (temp->next == NULL) {
        printf("Key not found\n");
        return;
    }

    newNode->next = temp->next;
    newNode->prev = temp;
    temp->next->prev = newNode;
    temp->next = newNode;
}

void traverse() {
    struct Node* temp = head;
    while (temp != NULL) {
        printf("%d ", temp->data);
        temp = temp->next;
    }
    printf("\n");
}

void reverse() {
    struct Node* temp = NULL;
    struct Node* current = head;

    while (current != NULL) {
        temp = current->prev;
        current->prev = current->next;
        current->next = temp;
        current = current->prev;
    }

    if (temp != NULL)
        head = temp->prev;
}

int main() {
    int choice, data, position, key;

    while (1) {
        printf("\n1. Insert at rear\n2. Delete from rear\n3. Insert at position\n");
        printf("4. Delete from position\n5. Insert after element\n6. Insert before element\n");
        printf("7. Traverse\n8. Reverse\n9. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                printf("Enter data to insert: ");
                scanf("%d", &data);
                insertRear(data);
                break;
            case 2:
                deleteRear();
                break;
            case 3:
                printf("Enter data to insert: ");
                scanf("%d", &data);
                printf("Enter position: ");
                scanf("%d", &position);
                insertPosition(data, position);
                break;
            case 4:
                printf("Enter position to delete: ");
                scanf("%d", &position);
                deletePosition(position);
                break;
            case 5:
                printf("Enter data to insert: ");
                scanf("%d", &data);
                printf("Enter element after which to insert: ");
                scanf("%d", &key);
                insertAfter(data, key);
                break;
            case 6:
                printf("Enter data to insert: ");
                scanf("%d", &data);
                printf("Enter element before which to insert: ");
                scanf("%d", &key);
                insertBefore(data, key);
                break;
            case 7:
                traverse();
                break;
            case 8:
                reverse();
                break;
            case 9:
                exit(0);
            default:
                printf("Invalid choice\n");
        }
    }

    return 0;
}