DSA · Theory

Stack Operations

Theory

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If you can teach Stack Operations using undo typing, you know it. If you only know the heading, you don’t.

Stack Operations order — meaning → push / pop LIFO → one limit. Dumping ten features helps nobody.

Stack Operations exists so Meera can keep undo typing correct in a tiny editor.

Stack Operations shows up in a tiny editor. Name undo typing, not “a real-world scenario”.

Stack Operations trap — pop on empty. Meera loses marks for that every viva.

Stack Operations is not a lonely heading. Meera ties it to undo typing.

Close Stack Operations with — “If I skip it, undo typing goes wrong like this: pop on empty.”

Diagram

    | 3 |  ← top (pop)
    | 2 |
    | 1 |
    LIFO

Exam tip

Board: undo typing. Dry-run Stack Operations. Name the trap: pop on empty.

stack = []
stack.append(10)   # push
stack.append(20)
print(stack.pop()) # 20
print(stack[-1])   # peek → 10

Stack Operations — stack is LIFO: push/pop from the same end.