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How can you reduce this problem to the classical Two Sum problem?
Do an in-order traversal of each tree to convert them to sorted arrays.
Solve the classical Two Sum problem.
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Yes, variations of this problem appear in technical interviews at major tech companies. It tests knowledge of BST traversal, hash-based lookups, and adapting the classic Two Sum pattern to tree structures.
A common optimal approach uses a hash set. Traverse the first BST and store its values in the set, then traverse the second BST and check if target minus the current value exists in the set. This provides linear time complexity relative to the total number of nodes.
Yes. By performing an inorder traversal on one BST and a reverse inorder traversal on the other, you can simulate a sorted ascending and descending sequence. This allows the two-pointer technique to efficiently check pairs that sum to the target.
A hash set is often the most practical data structure because it allows constant-time lookups for complements. Alternatively, stacks can be used to simulate inorder and reverse inorder traversals for a two-pointer style solution.
