DSA · Theory

AA tree

Theory

35/810

Sara only reaches for AA tree when folder on disk has to stay correct in a file explorer.

Do AA tree once by hand. left < root < right. Change one input. Say the new result out loud.

AA tree exists so Sara can keep folder on disk correct in a file explorer.

Sara ships AA tree in a file explorer. That is the use case worth saying.

Don’t do this with AA tree — unbalanced BST becoming a list. Interviewers spot it in ten seconds.

AA tree is not a lonely heading. Sara ties it to folder on disk.

Close AA tree with — “If I skip it, folder on disk goes wrong like this: unbalanced BST becoming a list.”

Exam tip

Board: folder on disk. Dry-run AA tree. Name the trap: unbalanced BST becoming a list.

# AA tree
data = [4, 1, 3]
print("start", data)
if data[0] > data[1]:
    data[0], data[1] = data[1], data[0]
print("after one step", data)

AA tree: dry-run [4, 1, 3]. Say the list after one step.