[Solved] Consider two approaches to flatten a binary tree: (1) Brute force preorder traversal collecting nodes in a list and rebuilding the linked list, and (2)... When is approach (1) preferable over (2)? | Tree: Depth-First Search

Tree: Depth-First Search - Flatten Binary Tree to Linked List

Consider two approaches to flatten a binary tree: (1) Brute force preorder traversal collecting nodes in a list and rebuilding the linked list, and (2) Optimal reverse preorder traversal with a global pointer. When is approach (1) preferable over (2)?

AWhen minimizing space usage is critical

BWhen the tree is very deep and recursion stack may overflow

CWhen in-place modification is required

DWhen the tree is balanced and small

Step-by-Step Solution

Solution:

Step 1: Compare space usage
Brute force uses O(n) extra space; optimal uses O(h) recursion stack.
Step 2: Identify when recursion stack overflow is a concern
Brute force approach avoids recursion stack, so preferable when tree is very deep and recursion stack may overflow.
Step 3: Determine preference
Approach (1) is preferable when recursion stack overflow risk exists.
Final Answer:
Option B -> Option B
Quick Check:
Brute force avoids recursion stack overflow [OK]

Quick Trick: Brute force avoids recursion stack overflow [OK]

Common Mistakes:

MISTAKES

Assuming brute force always better
Ignoring space trade-offs

Trap Explanation:

PITFALL

Candidates confuse space/time trade-offs and in-place constraints.

Interviewer Note:

CONTEXT

Tests understanding of trade-offs between approaches and constraints.

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More Tree: Depth-First Search Quizzes

When is approach (1) preferable over (2)?

Step 1: Compare space usage

Step 2: Identify when recursion stack overflow is a concern

Step 3: Determine preference

Final Answer:

Quick Check:

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