🚀 28. How do you implement a circular linked list?

In a circular linked list: Last node → points to head instead of NULL.

🔹 Visualization 
1 → 2 → 3 
↑       ↓ 
← ← ← ←

🔹 Python Example
class Node:
  def init(self, data):
    self.data = data
    self.next = None

head = Node(1)
second = Node(2)
third = Node(3)

head.next = second
second.next = third
third.next = head

🔹 Uses
✅ Round-robin scheduling
✅ Multiplayer games
✅ Music playlists
✅ CPU scheduling

🚀 29. How do you split a list into equal parts?

🔹 Approach
1. Count total nodes
2. Divide length
3. Break links carefully

🔹 Example
1 → 2 → 3 → 4 → 5 → 6

Split into 2 parts:
1 → 2 → 3
4 → 5 → 6

🔹 Python Idea
length = count_nodes(head)
part_size = length // k
extra = length % k

Distribute remaining nodes one by one.

🔹 Complexity
Time → O(n)
Space → O(1)

🔹 Interview Tip
Frequently appears in partitioning problems.

🚀 30. How do you implement a doubly linked list?
A doubly linked list stores: prev pointer + next pointer

🔹 Visualization
NULL ← 1 ⇄ 2 ⇄ 3 → NULL

🔹 Python Implementation
class Node:
  def init(self, data):
    self.data = data
    self.prev = None
    self.next = None

🔹 Advantages
✅ Bidirectional traversal
✅ Easier deletion
✅ Efficient backtracking

🔹 Disadvantages
❌ More memory
❌ Extra pointer management

🔹 Real-World Uses
✅ Browser history
✅ Undo/redo
✅ Navigation systems
✅ Music players

🔹 Complexity
Insert/Delete → O(1)
Search → O(n)

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