Free Practice Quiz Question List

5 Stacks and Queues Online Quiz Questions

Use this free practice quiz with 20 questions to review 5 Stacks and Queues, test your knowledge, and prepare for your next test or exam.

20 questions

Choose one

1 point

A stack is initially empty. The operations push(A), push(B), and push(C) are performed in that order. Which value is returned by the next pop()?

Choose one

1 point

A queue is initially empty. The operations enqueue(A), enqueue(B), and enqueue(C) are performed in that order. Which value is returned by the next dequeue()?

A
C
B
B
C
A
D
The value at the rear

Choose all

1 point

Select all situations for which a stack is the more natural abstraction.

A
Maintaining an undo history
B
Processing tasks fairly in arrival order
C
Exploring a graph depth-first
D
Serving requests in arrival order

Choose all

1 point

Select all design features that support an efficient fixed-capacity circular-array queue.

A
Wrap indices around with modular arithmetic.
B
Maintain the number of stored elements.
C
Shift every remaining element after each removal.
D
Keep only a rear pointer and no front position.

True or false

1 point

True or false: Omitting the rear pointer from a singly linked-list queue makes enqueue() take O(n) time because the list must be traversed to find its end.

A
True
B
False

True or false

1 point

True or false: In a naive array-based queue that shifts all remaining elements after each dequeue, one dequeue can take $O(n)$ time.

A
True
B
False

Written response

1 point

In a linked-list queue, what is the standard name of the pointer that identifies the insertion endpoint?

Written response

1 point

For a dynamically resized array stack that grows geometrically, what is the amortized time complexity of one $push()$ over a long sequence of insertions? Include the word “amortized” in your answer.

Fill in the blank

1 point

Complete the statements about a linked-list stack: push() and pop() each take time, and storing n elements requires space.

Fill in the blank

1 point

Under the array-stack convention described in the material, the integer represents the .

Choose one

1 point

Why do nested function calls return in LIFO order?

A
The outermost function always returns first.
B
The most recently called function returns first.
C
All calls return in the order they were made.
D
The call stack stores only global variables.

Choose one

1 point

Which implementation best avoids O(n) shifting when repeatedly removing items from the front of an array-backed queue?

A
A linked-list stack with a head pointer
B
A circular-array queue with modular index updates
C
A naive array queue that shifts after removal
D
A priority queue ordered by insertion cost

Choose one

1 point

What is the main purpose of treating an array as a circular buffer when implementing a queue?

A
It keeps every element permanently at index 0
B
It sorts elements before each insertion
C
It prevents the queue from ever becoming full
D
It allows the rear and front indices to wrap around and reuse array positions

Choose one

1 point

A queue is implemented with a singly linked list and both front and rear pointers. What is the time complexity of enqueue?

A
O(n), because every existing node must be copied
B
O(1), because the rear pointer identifies the insertion point
C
O(log n), because the nodes must be searched by value
D
O(n^2), because each node requires two traversals

Choose one

1 point

Which data structure is most appropriate for the frontier in breadth-first search, and why?

A
A stack, because the newest vertex must always be processed first
B
A deque, because BFS never processes vertices in layers
C
A queue, because vertices are processed in arrival order within each layer
D
A linked list used only for random-access lookup

Choose one

1 point

A stack uses a dynamically resized array whose capacity grows geometrically. What is the amortized time complexity of push over a long sequence of insertions?

A
The amortized time per push is O(1), although an individual resize can cost O(n).
B
Every push takes O(n), because the array may be copied on every insertion.
C
The amortized time per push is O(log n), because the capacity grows geometrically.
D
Every push takes O(n^2), because each resize copies all earlier arrays.

True or false

1 point

A deque can provide both queue behavior and stack behavior by choosing appropriate ends for insertion and removal.

A
True
B
False

Written response

1 point

What is the term for attempting to remove or examine an element from an empty stack or queue?

Written response

1 point

An initially empty queue performs enqueue(A), enqueue(B), enqueue(C), and then dequeue(). What is the queue size afterward?

Open ended

1 point

A compiler scans the delimiter sequence ([{}]) from left to right. Explain how a stack can be used to determine whether the sequence is balanced, and state why this particular sequence is accepted. Also explain what would make a delimiter sequence invalid.