How do you find the Lowest Common Ancestor in a general Binary Tree?
Similar to the BST version but without the ordering property, requiring a different approach.
Why Interviewers Ask This
This tests your ability to adapt algorithms when constraints (like BST ordering) are removed.
How to Answer This Question
Explain the recursive approach: search for p and q in left and right subtrees. If both are found in different subtrees, the root is LCA. If found in one, return that result. Discuss O(N) time complexity.
Key Points to Cover
- Recursive search in both subtrees
- Check if current node is one of the targets
- Combine results from children
- O(N) time complexity
Sample Answer
Without the BST property, I must search both subtrees recursively. I check if the current node is p or q. Then I search left and right. If both searches return non-null, the current node is the LCA. If only one returns n…
Common Mistakes to Avoid
- Assuming BST properties hold
- Returning the first common ancestor found
- Not handling the base case correctly
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