[Solved] Consider the following buggy code snippet for building a binary tree from preorder and inorder... Which line contains the subtle bug that can cause incorrect tree construction or infinite loops? | Tree: Depth-First Search

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

Consider the following buggy code snippet for building a binary tree from preorder and inorder traversals. Which line contains the subtle bug that can cause incorrect tree construction or infinite loops?

ALine where stack is initialized with root

BLine inside if block missing stack.append(node.left)

CLine where root is initialized with preorder[0]

DLine inside else block where inorder_index is incremented

Step-by-Step Solution

Step 1: Identify missing operation
Inside the if block, after creating node.left, the new node is not pushed onto the stack.
Step 2: Consequences of missing stack append
Without pushing, the algorithm loses track of the left subtree root, causing incorrect tree or infinite loops.
Final Answer:
Option B -> Option B
Quick Check:
Stack must track all nodes to correctly build tree [OK]

Quick Trick: Always push newly created nodes to stack to track subtree roots [OK]

Common Mistakes:

MISTAKES

Forgetting to push left child nodes
Incorrectly incrementing inorder_index
Misinitializing root or stack

Trap Explanation:

PITFALL

Missing stack append looks like a minor omission but breaks the entire iterative logic.

Interviewer Note:

CONTEXT

Tests attention to detail and understanding of stack role in iterative tree construction.

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More Tree: Depth-First Search Quizzes

Which line contains the subtle bug that can cause incorrect tree construction or infinite loops?

Step 1: Identify missing operation

Step 2: Consequences of missing stack append

Final Answer:

Quick Check:

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