Stack and queue operations

≈ 45 min

Stack and queue operations

A stack restricts access to the most recently added item: push adds to the top and pop removes from the top. A queue restricts access to the earliest item: enqueue adds at the back and dequeue removes from the front. These restrictions are useful because the data structure makes the required order explicit instead of leaving every caller to invent its own list behaviour.

Undo history naturally uses a stack because the last action is undone first. A print queue or help-desk arrival line normally uses a queue because earlier requests should be served first. Neither structure is automatically fair in every situation: a clinic may need a clearly documented priority queue rather than a pure arrival order.

Worked reasoning. Start with an empty stack. Push A, then B, then C. The first pop returns C because C was last in. Start with an empty queue, enqueue A, B and C. The first dequeue returns A because A arrived first. Write the contents from removal end to insertion end when explaining your trace.

Exam lens. State the operation order before naming a structure. Then trace additions and removals one at a time; most marks are lost by reversing one end of the data structure.

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Which statement is the most defensible principle for Stack and queue operations?

Choose a stack for last-in, first-out work and a queue for first-in, first-out work.

Treat an implementation detail as more important than the stated rule.

Assume one successful run proves the system is correct in every case.

Avoid recording assumptions, limits or failure conditions.

Enter the key term for Stack and queue operations. Which removal order serves the earliest arrival first?

A text editor needs to undo the most recent change first. Which structure matches the required removal order?

A stack, because undo removes the last action first.

Use a larger class or broader permission without stating a rule.

Trust the first output and skip a boundary or failure check.

Hide the decision so affected people cannot inspect it.

Name the concise safeguard or principle that completes this lesson’s scenario: A text editor needs to undo the most recent change first. Which structure matches the required removal order?