Start by clarifying the problem: confirm whether the tree is a binary search tree or a general binary tree, and whether nodes have parent pointers. For a general binary tree, use a recursive post-order traversal that returns the node if it matches either target, otherwise recurses into left and right subtrees; the first node where both sides return non-null is the LCA. Discuss time and space complexity, and mention iterative or parent-pointer alternatives if applicable.
Pro tip: Meta interviewers value clean, bug-free code and clear communication. Before coding, walk through a small example to validate your logic, and after coding, test edge cases like one node being an ancestor of the other or nodes not present in the tree.
Ask whether the tree is a BST or a general binary tree, whether nodes have parent pointers, and whether both nodes are guaranteed to be in the tree. This determines the optimal approach.
For a general binary tree without parent pointers, use a recursive post-order traversal. If parent pointers exist, you can find the intersection of paths to the root. For a BST, you can use the BST property to guide the search.
Describe the recursive function: if the current node is null or matches either target, return the current node. Recurse left and right; if both return non-null, the current node is the LCA; otherwise return the non-null child.
State that the time complexity is O(n) in the worst case, as each node is visited once, and space complexity is O(h) for the recursion stack, where h is the tree height.
Walk through a simple tree with nodes, including edge cases: one node is the ancestor of the other, nodes are in different subtrees, or one node is missing. Verify the algorithm returns the correct LCA.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.