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

Question 2

Consider a scenario where you need to implement a backtracking algorithm. Which stack implementation would be most suitable?

Double-ended stack (deque)
Persistent stack
Standard stack
Multi-stack implementation in a single array

Question 3

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

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

Question 4

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

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

Question 5

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

Question 6

In a persistent stack implementation using linked lists, what is the time complexity of performing a 'pop' operation on a stack with 'n' elements?

O(n)
O(log n)
O(1)
It depends on the implementation.

Question 7

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?

Using separate head and tail pointers that move towards each other.
Growing the stack from both ends towards the middle of the array.
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.

Question 8

In a multi-stack implementation using a single array, what technique is commonly used to indicate the boundaries between individual stacks?

Using pointers or indices to mark the top and/or bottom of each stack.
Maintaining separate arrays to track the top and bottom of each stack.
Employing a hash table to map stack identifiers to their corresponding array ranges.
Storing special delimiter characters within the array.

Question 9

What is a significant advantage of implementing multiple stacks within a single array compared to using separate arrays for each stack?

Simplified implementation due to using a single data structure.
Enhanced security by isolating individual stacks within the array.
Improved time complexity for push and pop operations.
Reduced space complexity, especially when stack sizes are unpredictable.

Question 10

How can you implement a deque using two stacks effectively?

Alternate between pushing elements onto the two stacks, maintaining a balance.
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.
Use one stack for the front half of the deque and the other for the rear half.

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

Question 2

Consider a scenario where you need to implement a backtracking algorithm. Which stack implementation would be most suitable?

Double-ended stack (deque)
Persistent stack
Standard stack
Multi-stack implementation in a single array

Question 3

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

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

Question 4

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

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

Question 5

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

Question 6

In a persistent stack implementation using linked lists, what is the time complexity of performing a 'pop' operation on a stack with 'n' elements?

O(n)
O(log n)
O(1)
It depends on the implementation.

Question 7

Using separate head and tail pointers that move towards each other.
Growing the stack from both ends towards the middle of the array.
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.

Question 8

In a multi-stack implementation using a single array, what technique is commonly used to indicate the boundaries between individual stacks?

Using pointers or indices to mark the top and/or bottom of each stack.
Maintaining separate arrays to track the top and bottom of each stack.
Employing a hash table to map stack identifiers to their corresponding array ranges.
Storing special delimiter characters within the array.

Question 9

What is a significant advantage of implementing multiple stacks within a single array compared to using separate arrays for each stack?

Simplified implementation due to using a single data structure.
Enhanced security by isolating individual stacks within the array.
Improved time complexity for push and pop operations.
Reduced space complexity, especially when stack sizes are unpredictable.

Question 10

How can you implement a deque using two stacks effectively?

Alternate between pushing elements onto the two stacks, maintaining a balance.
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.
Use one stack for the front half of the deque and the other for the rear half.

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