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Yes, variations of BST validation and traversal verification problems are common in FAANG-style interviews. They test understanding of tree properties, stack usage, and preorder traversal logic.
A stack is the most useful data structure for this problem. It helps simulate the traversal path of a BST and allows efficient tracking of ancestor nodes while validating preorder constraints.
The optimal approach uses a monotonic stack while tracking a lower bound for valid values. As you traverse the preorder array, popping elements represents moving up the tree to a right subtree. If a value ever falls below the allowed lower bound, the sequence is invalid.
Yes, the problem is typically solved without constructing the actual BST. Instead, algorithms rely on BST ordering rules and traversal properties to validate the sequence directly in linear time.