[Solved] Suppose you need to find the Lowest Common Ancestor in a binary tree where nodes can have multiple parents (i.e.... Which approach is best suited to handle this variant? | Tree: Depth-First Search

Tree: Depth-First Search - Lowest Common Ancestor of Binary Tree

Suppose you need to find the Lowest Common Ancestor in a binary tree where nodes can have multiple parents (i.e., the structure is a DAG, not a tree). Which approach is best suited to handle this variant?

AUse the standard recursive DFS approach for binary trees

BUse parent pointers and ancestor sets as in trees

CUse brute force path comparison in the DAG

DUse Tarjan's offline LCA algorithm adapted for DAGs

Step-by-Step Solution

Solution:

Step 1: Understand DAG structure
Nodes can have multiple parents, so tree-based assumptions fail.
Step 2: Evaluate approaches
Standard tree DFS and parent pointer methods do not apply directly to DAGs.
Step 3: Tarjan's offline LCA algorithm
Tarjan's algorithm can be adapted to DAGs to find LCAs efficiently offline.
Final Answer:
Option D -> Option D
Quick Check:
DAG requires specialized algorithms beyond brute force [OK]

Quick Trick: Tarjan's algorithm adapts to DAGs [OK]

Common Mistakes:

MISTAKES

Applying tree LCA methods directly to DAGs

Trap Explanation:

PITFALL

Candidates assume tree methods work on DAGs, causing incorrect results.

Interviewer Note:

CONTEXT

Tests ability to adapt LCA approach to graph variants

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Which approach is best suited to handle this variant?

Step 1: Understand DAG structure

Step 2: Evaluate approaches

Step 3: Tarjan's offline LCA algorithm

Final Answer:

Quick Check:

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