What is the Lowest Common Ancestor in a Binary Search Tree?
A DSA problem asking for the deepest node that has two given nodes as descendants in a BST.
Why Interviewers Ask This
This tests your understanding of BST properties (left < root < right) and tree traversal algorithms.
How to Answer This Question
Explain the BST property allows a greedy approach. Start at the root. If both nodes are smaller, go left. If both are larger, go right. If they split, the current node is the LCA. Discuss O(h) time complexity.
Key Points to Cover
- Leverage BST ordering property
- Greedy traversal from root
- Stop when paths diverge
- O(h) time complexity
Sample Answer
In a BST, the LCA can be found efficiently by leveraging the ordering property. Starting from the root, if both target nodes are smaller than the current node, I move to the left child. If both are larger, I move to the…
Common Mistakes to Avoid
- Treating it like a general binary tree search
- Ignoring the BST property
- Handling null nodes incorrectly
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