Tree: Depth-First Search - Construct Tree from Inorder and Postorder
If the postorder traversal array may contain duplicate values, which modification is essential to correctly reconstruct the binary tree from inorder and postorder traversals?
If the postorder traversal array may contain duplicate values, which modification is essential to correctly reconstruct the binary tree from inorder and postorder traversals?
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Step-by-Step Solution
Solution:
Step 1: Understand the problem with duplicates
Duplicates cause ambiguity in locating root indices in inorder traversal.Step 2: Use a mapping from value to all indices
Store all indices of each value in inorder traversal to correctly identify the root position during recursion.Step 3: Modify recursion to pick correct index instance
Track which occurrence of the duplicate value is being used to avoid ambiguity.Final Answer:
Option A -> Option AQuick Check:
Duplicates require multiple index tracking [OK]
Quick Trick: Map values to all inorder indices to handle duplicates [OK]
Common Mistakes:
MISTAKES- Assuming duplicates can be ignored
- Sorting traversal arrays which breaks tree structure
- Switching traversal types unnecessarily
Trap Explanation:
PITFALL- Ignoring duplicates causes incorrect root index lookup and wrong tree
Interviewer Note:
CONTEXT- Tests understanding of handling duplicates in tree reconstruction algorithms
Master "Construct Tree from Inorder and Postorder" in Tree: Depth-First Search
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