Main question was verifying whether a binary tree was a BST, given the function header that looked like public boolean isBST(root). He stated no other functions could be created and that child nodes did not have links to their parents.

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Anonymous · Accepted Answer

He was looking for me to use a helper function to pass the parent's value in.

boolean isBST(Node root) {
   return isBSTHelper(root.left, root.value, isLeft) && isBSTHelper(root.right, root.value, isRight);
}

something similar to this. Since he told me I could not use extra functions I could not come up with an answer which is why I am bitter / negative about this interview.

Khoa · Answer

Basically, what you would have in isBST is the stop condition (i.e. if left < current-node < right), then recursively whether isBST(left) && isBST(right) is true.

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