Tree: Depth-First Search - Lowest Common Ancestor of Binary Tree
In a binary tree, which method efficiently finds the lowest common ancestor (LCA) of two nodes p and q without storing parent pointers?
In a binary tree, which method efficiently finds the lowest common ancestor (LCA) of two nodes p and q without storing parent pointers?
easy💻 Programming Q1 of Q15
Step-by-Step Solution
Solution:
Step 1: Use recursive DFS
Traverse the tree recursively, returning the node if it matches p or q.Step 2: Backtrack and combine results
If both left and right recursive calls return non-null, current node is LCA.Final Answer:
Option C -> Option CQuick Check:
DFS finds LCA during recursion [OK]
Quick Trick: Use recursion to find LCA without extra storage [OK]
Common Mistakes:
MISTAKES- Assuming BFS is more efficient for LCA
- Using iterative traversal without parent pointers
- Storing all ancestors unnecessarily
Trap Explanation:
PITFALL- BFS and ancestor hash map approaches are less efficient without parent pointers
Interviewer Note:
CONTEXT- Tests understanding of recursive DFS approach for LCA without extra data structures
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