[Solved] During the recursive reconstruction of a binary tree from preorder and inorder traversals, which mistake in handling the inorder indices can lead to incorrect subtree boundaries and thus an invalid... | Tree: Depth-First Search

Tree: Depth-First Search - Construct Tree from Preorder and Inorder

During the recursive reconstruction of a binary tree from preorder and inorder traversals, which mistake in handling the inorder indices can lead to incorrect subtree boundaries and thus an invalid tree?

AUsing the preorder array instead of inorder array to find the root index

BNot updating the inorder start and end indices correctly for left and right subtree recursive calls

CSkipping the root node in the preorder traversal during recursion

DReversing the preorder traversal array before recursion

Step-by-Step Solution

Solution:

Step 1: Identify root from preorder
The first element in preorder is always the root of the current subtree.
Step 2: Find root index in inorder
Locate this root in the inorder array to split left and right subtrees.
Step 3: Update inorder boundaries correctly
Pass correct start and end indices for left and right subtree recursive calls to avoid overlapping or missing nodes.
Final Answer:
Option B -> Option B
Quick Check:
Incorrect boundaries cause infinite recursion or wrong tree structure [OK]

Quick Trick: Always update inorder boundaries precisely in recursion [OK]

Common Mistakes:

MISTAKES

Using global indices without adjusting for subtree limits
Confusing preorder and inorder arrays for root location
Not handling base cases properly leading to infinite recursion

Trap Explanation:

PITFALL

Other options seem plausible but do not cause infinite recursion or subtree boundary errors.

Interviewer Note:

CONTEXT

Tests understanding of recursive boundary management in tree reconstruction.

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More Tree: Depth-First Search Quizzes

During the recursive reconstruction of a binary tree from preorder and inorder traversals, which mistake in handling the inorder indices can lead to incorrect subtree boundaries and thus an invalid tree?

Step 1: Identify root from preorder

Step 2: Find root index in inorder

Step 3: Update inorder boundaries correctly

Final Answer:

Quick Check:

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