[Solved] Suppose you want to perform a preorder traversal on a binary tree where nodes can have parent pointers but... Which approach correctly adapts preorder traversal to this scenario without extra space? | Tree: Depth-First Search

Tree: Depth-First Search - Binary Tree Preorder Traversal

Suppose you want to perform a preorder traversal on a binary tree where nodes can have parent pointers but no left or right pointers. Which approach correctly adapts preorder traversal to this scenario without extra space?

AUse a modified iterative approach that tracks previously visited nodes to avoid revisiting

BUse recursion on parent pointers to simulate traversal

CIteratively traverse using parent pointers and a stack to track visited nodes

DUse Morris traversal by creating temporary threaded links on parent pointers

Step-by-Step Solution

Solution:

Step 1: Understand traversal constraints
Without left/right pointers, standard Morris or recursion is not applicable; parent pointers only allow upward traversal.
Step 2: Identify correct approach
Tracking previously visited nodes iteratively allows preorder traversal by moving up/down without extra space for recursion stack.
Final Answer:
Option A -> Option A
Quick Check:
Modified iterative approach handles parent-only trees without extra space [OK]

Quick Trick: Parent-only trees require tracking visited nodes iteratively [OK]

Common Mistakes:

MISTAKES

Trying to use recursion without child pointers
Attempting Morris traversal on parent pointers
Using stack without tracking visited nodes

Trap Explanation:

PITFALL

Naive recursion or Morris traversal fails without child pointers; tracking visited nodes is essential.

Interviewer Note:

CONTEXT

Tests candidate's ability to adapt traversal algorithms to non-standard tree representations.

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Which approach correctly adapts preorder traversal to this scenario without extra space?

Step 1: Understand traversal constraints

Step 2: Identify correct approach

Final Answer:

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