kiranpalsingh1806/coding-problems

1. Reverse Doubly Linked List

class Node {
  public:
      int data;
      Node* next;
      Node* prev;
};
 
void reverse(Node** head_ref) {
    Node* temp = NULL;
    Node* current = *head_ref;
 
    while (current != NULL) {
        temp = current->prev;
        current->prev = current->next;
        current->next = temp;
        current = current->prev;
    }
    
    if (temp != NULL) {
        *head_ref = temp->prev;
    }
}

void push(Node** head_ref, int new_data) {
    Node* new_node = new Node();
    new_node->data = new_data;
    new_node->prev = NULL;
    new_node->next = (*head_ref);
    if ((*head_ref) != NULL) {
      (*head_ref)->prev = new_node;
    }
    (*head_ref) = new_node;
}

void printList(Node* node) {
    while (node != NULL) {
        cout << node->data << " ";
        node = node->next;
    }
}

int main() {
    Node* head = NULL;
 
    push(&head, 2);
    push(&head, 4);
    push(&head, 8);
    push(&head, 10);
 
    cout << "Original Linked list" << endl;
    printList(head);
 
    reverse(&head);
 
    cout << "\nReversed Linked list" << endl;
    printList(head);
 
    return 0;
}