DSA · Theory

Sort a stack using a temporary stack

Theory

430/810

Sort a stack using a temporary stack is a DSA idea you prove with undo typing, not with a slogan.

Sort a stack using a temporary stack on the board: push / pop LIFO. Then say what undo typing looks like after.

Skip Sort a stack using a temporary stack and pop on empty shows up in a tiny editor.

Kabir ships Sort a stack using a temporary stack in a tiny editor. That is the use case worth saying.

Sort a stack using a temporary stack trap: pop on empty. Kabir loses marks for that every viva.

Sort a stack using a temporary stack is not a lonely heading. Kabir ties it to undo typing.

Viva for Sort a stack using a temporary stack: what it is → push / pop LIFO → the mistake (pop on empty).

Diagram

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

Exam tip

Board: undo typing. Dry-run Sort a stack using a temporary stack. Name the trap: pop on empty.

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

Sort a stack using a temporary stack — stack is LIFO: push/pop from the same end.

DefSort a stack using a temporary stack — Kabir uses it for undo typing in a tiny editor.
RuleSort a stack using a temporary stack → push / pop LIFO.
RememberSort a stack using a temporary stack + Big-O (a tiny editor).
UseSort a stack using a temporary stack in a tiny editor (undo typing).
TrapSort a stack using a temporary stack — pop on empty.
ExSort a stack using a temporary stack → undo typing.