> For the complete documentation index, see [llms.txt](https://mayanktyagi3111.gitbook.io/interview-prep/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mayanktyagi3111.gitbook.io/interview-prep/trees/binary-tree-to-a-circular-doubly-link-list.md).

# Binary Tree to a Circular Doubly Link List

Given a Binary Tree, convert it to a Circular Doubly Linked List (In-Place).

* The left and right pointers in nodes are to be used as previous and next pointers respectively in converted Circular Linked List.
* The order of nodes in List must be same as Inorder of the given Binary Tree.
* The first node of Inorder traversal must be head node of the Circular List.

**Example:**<br>

![](https://media.geeksforgeeks.org/wp-content/cdn-uploads/tree-to-list.png)

```java
class Solution {
    Node last;

    Node bToDLL(Node root) {
        if (root == null)
            return root;
        Node leftEnd = bToDLL(root.left);
        if (last != null) {
            last.right = root;
            root.left = last;
        }
        last = root;
        Node rightEnd = bToDLL(root.right);
        root.right = rightEnd;
        if (rightEnd != null)
            rightEnd.left = root;
        return leftEnd == null ? root : leftEnd;
    }

    Node bTreeToClist(Node root) {
        if (root == null)
            return root;
        Node head = bToDLL(root);
        head.left = last;
        last.right = head;
        return head;
    }
}
```