#include <iostream>
using namespace std;
class DoublyLinkedList {
private:
struct Node {
int data;
Node* prev;
Node* next;
};
Node* head;
Node* tail;
public:
DoublyLinkedList() {
head = NULL;
tail = NULL;
}
void insertBegin(int value) {
Node* newNode = new Node();
newNode->data = value;
newNode->prev = NULL;
newNode->next = NULL;
if (head == NULL) {
head = newNode;
tail = newNode;
} else {
newNode->next = head;
head->prev = newNode;
head = newNode;
}
}
void insertEnd(int value) {
Node* newNode = new Node();
newNode->data = value;
newNode->prev = NULL;
newNode->next = NULL;
if (head == NULL) {
head = newNode;
tail = newNode;
} else {
newNode->prev = tail;
tail->next = newNode;
tail = newNode;
}
}
void insertAfter(int key, int value) {
Node* newNode = new Node();
newNode->data = value;
newNode->prev = NULL;
newNode->next = NULL;
Node* current = head;
while (current != NULL) {
if (current->data == key) {
newNode->prev = current;
newNode->next = current->next;
if (current->next != NULL) {
current->next->prev = newNode;
} else {
tail = newNode;
}
current->next = newNode;
break;
}
current = current->next;
}
}
void insertByPosition(int position, int value) {
if (position <= 0) {
insertBegin(value);
} else if (position >= countNodes()) {
insertEnd(value);
} else {
Node* newNode = new Node();
newNode->data = value;
newNode->prev = NULL;
newNode->next = NULL;
Node* current = head;
for (int i = 0; i < position - 1; i++) {
current = current->next;
}
newNode->prev = current;
newNode->next = current->next;
current->next->prev = newNode;
current->next = newNode;
}
}
void deleteBegin() {
if (head == NULL) {
return;
}
Node* temp = head;
head = head->next;
if (head != NULL) {
head->prev = NULL;
} else {
tail = NULL;
}
delete temp;
}
void deleteEnd() {
if (tail == NULL) {
return;
}
Node* temp = tail;
tail = tail->prev;
if (tail != NULL) {
tail->next = NULL;
} else {
head = NULL;
}
delete temp;
}
void deleteAfter(int key) {
Node* current = head;
while (current != NULL) {
if (current->data == key && current->next != NULL) {
Node* temp = current->next;
current->next = temp->next;
if (temp->next != NULL) {
temp->next->prev = current;
} else {
tail = current;
}
delete temp;
break;
}
current = current->next;
}
}
void deleteByPosition(int position) {
if (position <= 0) {
deleteBegin();
} else if (position >= countNodes() - 1) {
deleteEnd();
} else {
Node* current = head;
for (int i = 0; i < position; i++) {
current = current->next;
}
Node* temp = current;
current->prev->next = current->next;
current->next->prev = current->prev;
delete temp;
}
}
void display() {
Node* current = head;
while (current != NULL) {
cout << current->data << " ";
current = current->next;
}
cout << endl;
}
private:
int countNodes() {
int count = 0;
Node* current = head;
while (current != NULL) {
count++;
current = current->next;
}
return count;
}
};
int main() {
DoublyLinkedList list;
int choice, value, key, position;
while (true) {
cout << "1. Insert at beginning\n"
<< "2. Insert at end\n"
<< "3. Insert after a specific element\n"
<< "4. Insert at a specific position\n"
<< "5. Delete from beginning\n"
<< "6. Delete from end\n"
<< "7. Delete the element after a specific element\n"
<< "8. Delete from a specific position\n"
<< "9. Display the list\n"
<< "10. Exit\n"
<< "Enter your choice: ";
cin >> choice;
switch (choice) {
case 1:
cout << "Enter the value to insert: ";
cin >> value;
list.insertBegin(value);
cout << "Element inserted at the beginning.\n";
break;
case 2:
cout << "Enter the value to insert: ";
cin >> value;
list.insertEnd(value);
cout << "Element inserted at the end.\n";
break;
case 3:
cout << "Enter the key element: ";
cin >> key;
cout << "Enter the value to insert: ";
cin >> value;
list.insertAfter(key, value);
cout << "Element inserted after " << key << ".\n";
break;
case 4:
cout << "Enter the position: ";
cin >> position;
cout << "Enter the value to insert: ";
cin >> value;
list.insertByPosition(position, value);
cout << "Element inserted at position " << position << ".\n";
break;
case 5:
list.deleteBegin();
cout << "Element deleted from the beginning.\n";
break;
case 6:
list.deleteEnd();
cout << "Element deleted from the end.\n";
break;
case 7:
cout << "Enter the key element: ";
cin >> key;
list.deleteAfter(key);
cout << "Element deleted after " << key << ".\n";
break;
case 8:
cout << "Enter the position: ";
cin >> position;
list.deleteByPosition(position);
cout << "Element deleted from position " << position << ".\n";
break;
case 9:
cout << "Current list: ";
list.display();
break;
case 10:
cout << "Exiting program.\n";
exit(0);
default:
cout << "Invalid choice. Please try again.\n";
}
}
return 0;
}
