How do you convert a Binary Tree to a Doubly Linked List?
A problem requiring in-place conversion of a tree structure to a circular or linear DLL.
Why Interviewers Ask This
Tests pointer manipulation skills and understanding of in-order traversal sequences.
How to Answer This Question
Explain using in-order traversal. Maintain a global 'prev' pointer. Link the current node to 'prev' and update 'prev'. Handle the head node separately. Discuss O(N) time and O(1) space.
Key Points to Cover
- Use In-Order Traversal
- Maintain a 'prev' pointer
- Update left and right pointers
- Handle head/tail connections
Sample Answer
I would use an in-order traversal to convert the tree. During the traversal, I maintain a reference to the previously visited node. For each node, I set its left pointer to the previous node and the previous node's right…
Common Mistakes to Avoid
- Creating a new list instead of in-place
- Forgetting to link the last node
- Incorrectly managing the prev pointer
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