Tree: Depth-First Search - Flatten Binary Tree to Linked List
Which traversal method is essential to flatten a binary tree into a linked list that preserves the preorder node sequence without using extra space?
Which traversal method is essential to flatten a binary tree into a linked list that preserves the preorder node sequence without using extra space?
easy💻 Programming Q1 of Q15
Step-by-Step Solution
Solution:
Step 1: Understand preorder traversal order
Preorder visits nodes in root-left-right order, which matches the desired linked list sequence.Step 2: Use reverse preorder traversal
Reverse preorder (right-left-root) allows flattening from bottom up, rewiring pointers in-place.Step 3: Pointer rewiring
At each node, set its right pointer to the previously processed node and left pointer to null.Final Answer:
Option C -> Option CQuick Check:
Preorder order preserved by reverse traversal [OK]
Quick Trick: Reverse preorder traversal rewires pointers in-place [OK]
Common Mistakes:
MISTAKES- Using inorder traversal which does not preserve preorder sequence
- Using extra data structures unnecessarily
- Confusing postorder with preorder traversal
Trap Explanation:
PITFALL- Other traversals do not maintain preorder sequence or require extra space
Interviewer Note:
CONTEXT- Tests understanding of traversal order and in-place pointer manipulation
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