#include <iostream>
using namespace std;
class node {
public:
int data;
node* next;
node* prev;
node(int val) {
data = val;
next = prev = nullptr;
}
};
void insertAtHead(node* &head, int val) {
node* n = new node(val);
n->next = head;
if (head != nullptr) {
head->prev = n;
}
head = n;
}
void deleteAtHead(node* &head) {
if (head == nullptr) {
return;
}
node* todelete = head;
head = head->next;
if (head != nullptr) {
head->prev = nullptr;
}
delete todelete;
}
void deletion(node* &head, int val) {
if (head == nullptr) {
return;
}
if (head->data == val) {
deleteAtHead(head);
return;
}
node* temp = head;
while (temp->next != nullptr && temp->next->data != val) {
temp = temp->next;
}
if (temp->next == nullptr) {
return;
}
node* todelete = temp->next;
temp->next = todelete->next;
if (todelete->next != nullptr) {
todelete->next->prev = temp;
}
delete todelete;
}
void insertAtTail(node* &head, int val) {
node* n = new node(val);
if (head == nullptr) {
head = n;
} else {
node* temp = head;
while (temp->next != nullptr) {
temp = temp->next;
}
temp->next = n;
n->prev = temp;
}
}
void display(node* head) {
node* temp = head;
while (temp != nullptr) {
cout << temp->data << " <-> ";
temp = temp->next;
}
cout << "NULL" << endl;
}
int main() {
node* head = nullptr;
insertAtTail(head, 1);
insertAtTail(head, 2);
insertAtHead(head, 3);
insertAtTail(head, 4);
cout << "Before deletion: ";
display(head);
deleteAtHead(head);
cout << "After deletion: ";
display(head);
return 0;
}
