DSA · Theory

Substring Check

Theory

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Substring Check is a DSA topic. In plain words you use it for folder on disk in a file explorer. Don’t start with a slogan — start with that picture.

Smallest example: left < root < right. Type it, run it, and say what you see. If you can do that from memory, you know Substring Check.

From the example next to this theory — Substring Check: dry-run [4, 1, 3].

Trap — unbalanced BST becoming a list. Fix that before you talk about advanced DSA.

Viva — what is Substring Check? Then show left < root < right. Then name the trap.

Diagram

Exam tip

What is Substring Check? Show this: left < root < right. Trap: unbalanced BST becoming a list.

# Substring Check
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)

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