Prepare for Stacks Data Structure Interview with iQwizz | Difficulty Level: Advance | Rating: 4.6

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Question 1

Which of these scenarios would particularly benefit from using a persistent stack?

Managing function call stacks in a recursive algorithm.
Implementing undo/redo functionality in a text editor.
Representing the order of web pages visited in a browser's history.
Storing a dynamically changing list of tasks in a to-do app.

Question 2

In a persistent stack implementation, what happens when you push a new element onto the stack?

The original stack is modified to include the new element.
A new stack is created with the new element, preserving the original stack.
An error occurs as persistent stacks are immutable.
The new element replaces the top element of the original stack.

Question 3

How can you implement a deque using two stacks effectively?

Use one stack for enqueuing and the other for dequeuing, transferring elements when one stack is empty.
Store the deque elements in both stacks simultaneously for redundancy.
Alternate between pushing elements onto the two stacks, maintaining a balance.
Use one stack for the front half of the deque and the other for the rear half.

Question 4

You are tasked with designing a double-ended stack using a fixed-size array. Which of the following strategies is MOST likely to result in frequent stack overflows, even when the total number of elements in the stack is significantly less than the array's capacity?

Growing the stack from one end and allowing the other end to wrap around when it reaches the array boundary.
Resizing the array dynamically whenever an overflow occurs.
Growing the stack from both ends towards the middle of the array.
Using separate head and tail pointers that move towards each other.

Question 5

What is an advantage of using a persistent stack in a concurrent programming environment?

Reduces the risk of race conditions and data inconsistencies.
Simplifies data sharing and communication between threads.
Eliminates the need for locks or synchronization primitives.
Improves performance by allowing parallel access to the stack.

Question 6

In the largest rectangle in a histogram problem, we aim to find the rectangle with the maximum area within a given histogram. How does the stack help in efficiently determining the area of potential rectangles?

The stack stores the heights of the bars in increasing order, allowing for quick area calculation.
The stack maintains the areas of all previously encountered rectangles for comparison.
The stack is not used in the most efficient solutions to this problem.
The stack keeps track of the starting indices of potential rectangles, enabling efficient width calculation.

Question 7

Which of the following scenarios is MOST likely to benefit from using a persistent stack data structure?

Managing function call stacks in a recursive algorithm.
All of the above.
Implementing an undo/redo functionality in a text editor.
Storing a history of user actions for analytics purposes.

Question 8

What is the primary challenge in implementing multiple stacks within a single array?

Managing the dynamic resizing of the array as stacks grow and shrink.
Optimizing the search operation across all stacks stored in the array.
Maintaining the order of elements within each individual stack.
Ensuring data integrity and preventing data corruption between stacks.

Question 9

The stock span problem requires finding the number of consecutive days before each day with a stock price less than or equal to the current day's price. What is the time complexity of the most efficient algorithm for this problem using a stack?

O(n)
O(1)
O(n^2)
O(n log n)

Question 10

What is the fundamental idea behind memory optimization in stack implementations that use linked lists?

Storing only the difference between consecutive values in the stack, reducing the memory required per node.
Using a tail pointer in addition to the head pointer to facilitate faster memory deallocation during pop operations.
Relying on the operating system's virtual memory management to handle memory allocation and deallocation efficiently.
Pre-allocating a large block of memory for stack nodes to reduce the overhead of individual allocations.

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Question 1

Which of these scenarios would particularly benefit from using a persistent stack?

Managing function call stacks in a recursive algorithm.
Implementing undo/redo functionality in a text editor.
Representing the order of web pages visited in a browser's history.
Storing a dynamically changing list of tasks in a to-do app.

Question 2

In a persistent stack implementation, what happens when you push a new element onto the stack?

The original stack is modified to include the new element.
A new stack is created with the new element, preserving the original stack.
An error occurs as persistent stacks are immutable.
The new element replaces the top element of the original stack.

Question 3

How can you implement a deque using two stacks effectively?

Use one stack for enqueuing and the other for dequeuing, transferring elements when one stack is empty.
Store the deque elements in both stacks simultaneously for redundancy.
Alternate between pushing elements onto the two stacks, maintaining a balance.
Use one stack for the front half of the deque and the other for the rear half.

Question 4

Growing the stack from one end and allowing the other end to wrap around when it reaches the array boundary.
Resizing the array dynamically whenever an overflow occurs.
Growing the stack from both ends towards the middle of the array.
Using separate head and tail pointers that move towards each other.

Question 5

What is an advantage of using a persistent stack in a concurrent programming environment?

Reduces the risk of race conditions and data inconsistencies.
Simplifies data sharing and communication between threads.
Eliminates the need for locks or synchronization primitives.
Improves performance by allowing parallel access to the stack.

Question 6

The stack stores the heights of the bars in increasing order, allowing for quick area calculation.
The stack maintains the areas of all previously encountered rectangles for comparison.
The stack is not used in the most efficient solutions to this problem.
The stack keeps track of the starting indices of potential rectangles, enabling efficient width calculation.

Question 7

Which of the following scenarios is MOST likely to benefit from using a persistent stack data structure?

Managing function call stacks in a recursive algorithm.
All of the above.
Implementing an undo/redo functionality in a text editor.
Storing a history of user actions for analytics purposes.

Question 8

What is the primary challenge in implementing multiple stacks within a single array?

Managing the dynamic resizing of the array as stacks grow and shrink.
Optimizing the search operation across all stacks stored in the array.
Maintaining the order of elements within each individual stack.
Ensuring data integrity and preventing data corruption between stacks.

Question 9

O(n)
O(1)
O(n^2)
O(n log n)

Question 10

What is the fundamental idea behind memory optimization in stack implementations that use linked lists?

Storing only the difference between consecutive values in the stack, reducing the memory required per node.
Using a tail pointer in addition to the head pointer to facilitate faster memory deallocation during pop operations.
Relying on the operating system's virtual memory management to handle memory allocation and deallocation efficiently.
Pre-allocating a large block of memory for stack nodes to reduce the overhead of individual allocations.

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