How do you find the Lowest Common Ancestor in a BST vs binary tree?

Short answer: BST: walk from root — if both values are smaller go left, both larger go right, else current is LCA. General binary tree: recurse; if both sides return non-null, current is LCA; else return the non-null side.

Complexity

BST average O(h); general tree O(n).

Ask which tree type — the optimal approach changes.