Quick sort MCQs

By: Prof. Dr. Fazal Rehman Shamil | Last updated: September 20, 2024

 

What is the primary purpose of Quick Sort?
A) To search for an element
B) To sort an array
C) To merge two arrays
D) To partition data
Answer: B) To sort an array

What is the average-case time complexity of Quick Sort?
A) O(n)
B) O(n log n)
C) O(n^2)
D) O(log n)
Answer: B) O(n log n)

Which of the following best describes the Quick Sort algorithm?
A) It repeatedly swaps adjacent elements.
B) It selects a pivot and partitions the array.
C) It sorts the array in place without additional memory.
D) It merges sorted arrays.
Answer: B) It selects a pivot and partitions the array.

What is the worst-case time complexity of Quick Sort?
A) O(n)
B) O(n log n)
C) O(n^2)
D) O(log n)
Answer: C) O(n^2)

Which of the following is true about the stability of Quick Sort?
A) It is a stable sorting algorithm.
B) It is not a stable sorting algorithm.
C) It can only sort numerical data.
D) It requires additional memory for stability.
Answer: B) It is not a stable sorting algorithm.

What is the space complexity of Quick Sort?
A) O(1)
B) O(n)
C) O(n log n)
D) O(n^2)
Answer: A) O(log n)

What is the main advantage of Quick Sort over other sorting algorithms?
A) It is always faster than Merge Sort.
B) It requires less memory.
C) It can sort linked lists efficiently.
D) It is a stable sorting algorithm.
Answer: B) It requires less memory.

Which of the following is a common method for choosing a pivot in Quick Sort?
A) First element
B) Last element
C) Median of three
D) Random element
Answer: C) Median of three

In Quick Sort, what happens if the pivot is the smallest or largest element?
A) The algorithm will be very efficient.
B) The algorithm will perform poorly, resulting in O(n^2) complexity.
C) The array will remain unchanged.
D) The algorithm will terminate immediately.
Answer: B) The algorithm will perform poorly, resulting in O(n^2) complexity.

How does Quick Sort compare to Merge Sort in terms of worst-case performance?
A) Quick Sort has worse performance.
B) Merge Sort has worse performance.
C) Both have the same performance.
D) It depends on the implementation.
Answer: A) Quick Sort has worse performance.

What will be the output of Quick Sort if applied to the array [9, 7, 5, 11, 12, 2, 14]?
A) [2, 5, 7, 9, 11, 12, 14]
B) [14, 12, 11, 9, 7, 5, 2]
C) [9, 7, 5, 11, 12, 2, 14]
D) [2, 11, 5, 14, 12, 9, 7]
Answer: A) [2, 5, 7, 9, 11, 12, 14]

What happens to the time complexity of Quick Sort for an already sorted array?
A) It improves to O(n).
B) It remains O(n log n).
C) It worsens to O(n^2).
D) It stays O(log n).
Answer: C) It worsens to O(n^2).

Which of the following best describes the partitioning step in Quick Sort?
A) It divides the array into equal halves.
B) It rearranges elements based on the pivot.
C) It merges two sorted arrays.
D) It randomly shuffles the elements.
Answer: B) It rearranges elements based on the pivot.

What is the primary disadvantage of Quick Sort?
A) It is unstable.
B) It is inefficient for small datasets.
C) It can have poor performance on certain inputs.
D) It requires additional memory.
Answer: C) It can have poor performance on certain inputs.

What is the main characteristic of the Quick Sort algorithm?
A) It is not recursive.
B) It is based on the divide and conquer strategy.
C) It requires a large amount of memory for sorting.
D) It is adaptive for partially sorted data.
Answer: B) It is based on the divide and conquer strategy.

What is the result of applying Quick Sort to an empty array?
A) An error occurs.
B) The empty array remains unchanged.
C) The algorithm cannot sort it.
D) The array will be filled with zeros.
Answer: B) The empty array remains unchanged.

In Quick Sort, what happens during the partitioning phase?
A) Elements are merged into a sorted array.
B) The pivot is chosen and elements are rearranged.
C) The array is divided into equal halves.
D) Elements are sorted in descending order.
Answer: B) The pivot is chosen and elements are rearranged.

Which data structure is typically used to implement Quick Sort?
A) Array
B) Linked List
C) Tree
D) Graph
Answer: A) Array

How does Quick Sort perform with datasets that are nearly sorted?
A) It is less efficient.
B) It remains O(n log n).
C) It becomes adaptive.
D) It performs worse than Merge Sort.
Answer: B) It remains O(n log n).

Which technique can be used to improve the performance of Quick Sort?
A) Randomized pivot selection
B) Always using the first element as pivot
C) Limiting the recursion depth
D) Using an auxiliary array
Answer: A) Randomized pivot selection

In which scenario does Quick Sort perform best?
A) When the array is nearly sorted
B) When the array contains many duplicate elements
C) When the pivot is chosen randomly
D) When the array is sorted in reverse order
Answer: C) When the pivot is chosen randomly

What is the output of Quick Sort on the array [3, 6, 8, 10, 1, 2, 1]?
A) [1, 1, 2, 3, 6, 8, 10]
B) [10, 8, 6, 3, 2, 1, 1]
C) [3, 6, 8, 10, 1, 2, 1]
D) [1, 2, 3, 6, 8, 10]
Answer: A) [1, 1, 2, 3, 6, 8, 10]

What happens if Quick Sort is implemented with a bad pivot choice consistently?
A) The sorting becomes faster.
B) The sorting takes longer and may approach O(n^2).
C) The algorithm fails to sort.
D) The array remains unchanged.
Answer: B) The sorting takes longer and may approach O(n^2).

What is the main operation performed during the partitioning process of Quick Sort?
A) Comparing
B) Swapping
C) Merging
D) Selecting
Answer: B) Swapping

What would be the output of Quick Sort on the array [5, 5, 5, 5, 5]?
A) [5, 5, 5, 5, 5]
B) [5, 5, 5, 5]
C) An error occurs.
D) The array becomes empty.
Answer: A) [5, 5, 5, 5, 5]

How does Quick Sort handle duplicate elements?
A) It ignores them.
B) It sorts them randomly.
C) It handles them like any other element.
D) It requires special treatment.
Answer: C) It handles them like any other element.

In Quick Sort, which of the following is a common choice for the pivot?
A) The smallest element
B) The median element
C) The largest element
D) The middle element
Answer: D) The middle element

Which of the following scenarios would Quick Sort not perform well?
A) Sorted array
B) Array with many duplicate elements
C) Randomly ordered array
D) Nearly sorted array
Answer: A) Sorted array

What happens during the recursive calls of Quick Sort?
A) The array is merged.
B) Subarrays are sorted.
C) Elements are swapped randomly.
D) The algorithm terminates.
Answer: B) Subarrays are sorted.

What is the typical recursive depth of Quick Sort in the average case?
A) O(1)
B) O(n)
C) O(log n)
D) O(n log n)
Answer: C) O(log n)

Which of the following statements is true about Quick Sort?
A) It can be implemented iteratively.
B) It always sorts in-place.
C) It is not suitable for large datasets.
D) It can be implemented with a linked list efficiently.
Answer: A) It can be implemented iteratively.

Which of the following is a variant of Quick Sort?
A) Heap Sort
B) Dual-Pivot Quick Sort
C) Merge Sort
D) Bubble Sort
Answer: B) Dual-Pivot Quick Sort

How is Quick Sort generally implemented?
A) Using recursion
B) Using iteration only
C) Using a combination of both
D) Not implemented in practice
Answer: A) Using recursion

What is the impact of the pivot choice on Quick Sort performance?
A) It has no impact.
B) A good choice can lead to O(n log n) performance, while a bad choice can lead to O(n^2).
C) A bad choice always leads to O(log n) performance.
D) It only affects space complexity.
Answer: B) A good choice can lead to O(n log n) performance, while a bad choice can lead to O(n^2).

When is Quick Sort preferred over Merge Sort?
A) When stability is required.
B) When memory usage is a concern.
C) When the dataset is very large.
D) When all elements are unique.
Answer: B) When memory usage is a concern.

What does Quick Sort do when it encounters subarrays of size one or zero?
A) It continues sorting.
B) It stops the recursion.
C) It merges them.
D) It throws an error.
Answer: B) It stops the recursion.

Which of the following is not a valid characteristic of Quick Sort?
A) It can be implemented with a randomized pivot.
B) It sorts by comparing elements directly.
C) It always requires additional space.
D) It divides the array into smaller subarrays.
Answer: C) It always requires additional space.

What is the significance of the partitioning index in Quick Sort?
A) It is the final sorted position of the pivot.
B) It indicates the number of elements sorted.
C) It determines the depth of recursion.
D) It does not affect the sorting.
Answer: A) It is the final sorted position of the pivot.

What is the effect of using a poor pivot selection strategy in Quick Sort?
A) It always leads to O(log n) performance.
B) It may lead to unbalanced partitions and degrade performance.
C) It has no effect on performance.
D) It makes Quick Sort stable.
Answer: B) It may lead to unbalanced partitions and degrade performance.