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

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Question 1

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

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

Question 2

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

Question 3

Imagine you're implementing a stack with a fixed-size array. Which situation leads to a stack overflow even if the number of elements in the stack is less than the array's size?

Pushing an element when the stack pointer is at the middle of the array.
Popping an element when the stack pointer is at the beginning of the array.
Pushing an element when the stack pointer is at the end of the array, even if some initial array slots are empty.
Popping an element when the stack pointer is at the end of the array.

Question 4

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

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

Question 5

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

Relying on the operating system's virtual memory management to handle memory allocation and deallocation efficiently.
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.
Pre-allocating a large block of memory for stack nodes to reduce the overhead of individual allocations.

Question 6

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.
Implementing an undo/redo functionality in a text editor.
Storing a history of user actions for analytics purposes.
All of the above.

Question 7

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

Employing a hash table to map stack identifiers to their corresponding array ranges.
Storing special delimiter characters within the array.
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.

Question 8

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

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

Question 9

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?

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.
Growing the stack from one end and allowing the other end to wrap around when it reaches the array boundary.

Question 10

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

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Question 1

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

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

Question 2

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

Question 3

Imagine you're implementing a stack with a fixed-size array. Which situation leads to a stack overflow even if the number of elements in the stack is less than the array's size?

Pushing an element when the stack pointer is at the middle of the array.
Popping an element when the stack pointer is at the beginning of the array.
Pushing an element when the stack pointer is at the end of the array, even if some initial array slots are empty.
Popping an element when the stack pointer is at the end of the array.

Question 4

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

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

Question 5

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

Relying on the operating system's virtual memory management to handle memory allocation and deallocation efficiently.
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.
Pre-allocating a large block of memory for stack nodes to reduce the overhead of individual allocations.

Question 6

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.
Implementing an undo/redo functionality in a text editor.
Storing a history of user actions for analytics purposes.
All of the above.

Question 7

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

Employing a hash table to map stack identifiers to their corresponding array ranges.
Storing special delimiter characters within the array.
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.

Question 8

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

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

Question 9

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.
Growing the stack from one end and allowing the other end to wrap around when it reaches the array boundary.

Question 10

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

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