Added a file of double linked list in c++

Data Structures/DoublyLinkedList.cpp

@@ -0,0 +1,206 @@
+// Doubly Linked List
+#include <iostream>
+using namespace std;
+class Node
+{
+public:
+    int data;
+    Node *next;
+    Node *prev;
+    Node(int data)
+    {
+        this->data = data;
+        this->next = NULL;
+        this->prev = NULL;
+    }
+    ~Node()
+    {
+        int value = this->data;
+        // memory free message
+        if (this->next != NULL)
+        {
+            delete next;
+            this->next = NULL;
+        }
+        cout << "Memory is free for node with data " << value << endl;
+    }
+};
+void print(Node *head, Node *tail)
+{
+    Node *temp = head;
+    while (temp != NULL)
+    {
+        cout << temp->data << " ";
+        temp = temp->next;
+    }
+    cout << endl;
+    cout << "head = " << head->data << " and tail = " << tail->data << endl
+         << endl;
+}
+
+int getLength(Node *head)
+{
+    int length = 0;
+    Node *temp = head;
+    while (temp != NULL)
+    {
+        length++;
+        temp = temp->next;
+    }
+    return length;
+}
+
+void insertAtHead(Node *&tail, Node *&head, int data)
+{
+    if (head == NULL)
+    {
+        Node *temp = new Node(data);
+        head = temp;
+        tail = temp;
+    }
+    else
+    {
+        Node *temp = new Node(data);
+        temp->next = head;
+        head->prev = temp;
+        head = temp;
+    }
+}
+
+void insertAtTail(Node *&tail, Node *&head, int data)
+{
+    if (tail == NULL)
+    {
+        Node *temp = new Node(data);
+        head = temp;
+        tail = temp;
+    }
+
+    Node *temp = new Node(data);
+    tail->next = temp;
+    temp->prev = tail->next;
+    tail = temp;
+}
+
+void insertAtPosition(Node *&tail, Node *&head, int position, int d)
+{
+    if (position == 1)
+    {
+        insertAtHead(tail, head, d);
+        return;
+    }
+    Node *temp = head;
+    int cnt = 1;
+    while (cnt < position - 1)
+    {
+        temp = temp->next;
+        cnt++;
+    }
+
+    // inserting at last position
+    if (temp->next == NULL)
+    {
+        insertAtTail(tail, head, d);
+        return;
+    }
+
+    // creating a node for d
+    Node *nodeToInsert = new Node(d);
+
+    nodeToInsert->next = temp->next;
+    temp->next->prev = nodeToInsert;
+    temp->next = nodeToInsert;
+    nodeToInsert->prev = temp;
+}
+
+void deleteNode(int position, Node *&head)
+{
+
+    if (position == 1)
+
+    {
+        Node *temp = head;
+        temp->next->prev = NULL;
+        head = temp->next;
+        temp->next = NULL;
+        delete temp;
+    }
+    else
+    {
+        Node *curr = head;
+        Node *prev = NULL;
+        int count = 1;
+        while (count < position)
+        {
+            prev = curr;
+            curr = curr->next;
+            count++;
+        }
+        // Order is important
+        curr->prev = NULL;
+        prev->next = curr->next;
+        curr->next = NULL;
+        /*
+
+Using curr->next->prev = NULL; is incorrect because it breaks the backward link
+of the doubly linked list. You should instead use curr->next->prev = prev; to ensure
+the list remains correctly linked.
+
+
+chatgpt
+
+5 <-> 10 <-> 15 <-> 20 <-> 25
+   ^         ^        ^        ^
+  prev      curr    next
+
+prev->next = curr->next;   // 10.next = 20
+curr->next->prev = prev;   // 20.prev = 10
+curr->next = NULL;        // 15.next = NULL
+curr->prev = NULL;        // 15.prev = NULL
+
+5 <-> 10 <-> 20 <-> 25
+   ^        ^
+  prev     next
+
+*/
+
+        delete curr;
+    }
+}
+
+int main()
+{
+    Node *node1 = new Node(10);
+    Node *head = node1;
+    Node *tail = node1;
+    print(head, tail);
+
+    insertAtHead(tail, head, 15);
+    print(head, tail);
+
+    insertAtPosition(tail, head, 2, 29);
+    print(head, tail);
+
+    deleteNode(2, head);
+    print(head, tail);
+
+    // Node *head = NULL; to handle these we made those if else
+    // Node *tail = NULL;
+    // print(head);
+
+    // cout << "Length of Doubly Linkedlist is " << getLength(head) << endl;
+
+    /*insertAtHead(tail, head, 15);
+    print(head,tail);
+
+    insertAtTail(tail, head, 20);
+    print(head,tail);
+
+    insertAtPosition(tail, head, 3, 29);
+    print(head,tail);
+
+    deleteNode(1, head);
+    print(head,tail);*/
+
+    return 0;
+}