Update DoublyLL.cpp

c++/DoublyLL.cpp

@@ -1,60 +1,82 @@
 #include <iostream>
 using namespace std;
+
+// Definition of Node class for Doubly Linked List
 class Node
 {
 public:
     Node *previous;
     int data;
     Node *next;
 };
-Node *Insert(int pos,int x, Node *head)
+
+// Function to insert a node at a given position
+Node *Insert(int pos, int x, Node *head)
 {
-     Node *t,*p;
-     if(pos ==0)
-     {
-        t=new Node;
-        t->data=x;
-        t->previous=NULL;
-        t->next=head;
-        if(head !=NULL)
-        head->previous=t;
-        head=t;
-     }
-     else
-     {
-        p=head;
-        for(int i=0;i<pos-1;i++)
-            p=p->next;
-        t=new Node;
-        t->data=x;
-        t->previous=p;
-        t->next=p->next;
-        if(p->next)
-        p->next->previous=t;
-        p->next=t;
-     }
-     return head;
+    Node *t, *p;
+    // Insert at the beginning (position 0)
+    if (pos == 0)
+    {
+        t = new Node;
+        t->data = x;
+        t->previous = NULL;   // New node's previous is NULL
+        t->next = head;       // New node points to current head
+
+        if (head != NULL)
+            head->previous = t; // Update the old head's previous pointer to the new node
+
+        head = t;              // Update head to the new node
+    }
+    // Insert at any position other than 0
+    else
+    {
+        p = head;
+        for (int i = 0; i < pos - 1; i++)
+            p = p->next;        // Traverse to the node before the insertion point
+
+        t = new Node;
+        t->data = x;
+        t->previous = p;        // New node's previous points to current node
+        t->next = p->next;      // New node's next points to current node's next
+
+        if (p->next)
+            p->next->previous = t; // Update the next node's previous pointer to the new node
+
+        p->next = t;            // Update current node's next to the new node
+    }
+    return head;                // Return updated head pointer
 }
+
+// Function to display the doubly linked list
 void display(Node *head)
 {
-    Node *p=head;
-    while(p!=NULL)
+    Node *p = head;
+    while (p != NULL)
     {
-        cout<<p->data<<" ";
-        p=p->next;
+        cout << p->data << " ";
+        p = p->next;  // Move to the next node
     }
+    cout << endl;  // Print newline after the list is displayed
 }
+
 int main()
 {
-    Node *first=NULL;
-    int n,x,pos;
-    cout<<"Enter the number of elements in the list: ";
-    cin>>n;
-    for(int i=0;i<n;i++)
+    Node *first = NULL;   // Initialize the head of the linked list
+    int n, x, pos;
+
+    // Input the number of elements to insert
+    cout << "Enter the number of elements in the list: ";
+    cin >> n;
+
+    // Insert elements into the list
+    for (int i = 0; i < n; i++)
     {
-        cin>>x;
-        first=Insert(i,x,first);
+        cin >> x;               // Input value to insert
+        first = Insert(i, x, first); // Insert at position i
     }
+
+    // Display the resulting list
     display(first);
-return 0;
-}
+
+    return 0;
+}