Top MCQs on QuickSort Algorithm with Answers

Question 11

Which of the following is true about merge sort?

• Merge Sort works better than quick sort if data is accessed from slow sequential memory.

• Merge Sort is stable sort by nature

• Merge sort outperforms heap sort in most of the practical situations.

• All of the above.

Question 12

Given an array where numbers are in range from 1 to n⁶, which sorting algorithm can be used to sort these number in linear time?

• Not possible to sort in linear time
• Radix Sort
• Counting Sort
• Quick Sort

Question 13

Which one of the following in place sorting algorithms needs the minimum number of swaps?

• Quick sort

• Insertion sort

• Selection sort

• Heap sort

Question 14

Suppose we have a O(n) time algorithm that finds median of an unsorted array. Now consider a QuickSort implementation where we first find median using the above algorithm, then use median as pivot. What will be the worst case time complexity of this modified QuickSort.

• O(n^2 Logn)
• O(n^2)
• O(n Logn Logn)
• O(nLogn)

Question 15

A machine needs a minimum of 100 sec to sort 1000 names by quick sort. The minimum time needed to sort 100 names will be approximately

• 50.2 sec
• 6.7 sec
• 72.7 sec
• 11.2 sec

Question 16

In quick sort, for sorting n elements, the (n/4)th smallest element is selected as a pivot using an O(n) time algorithm. What is the worst-case time complexity of the quick sort?

(A) θ(n)

(B) θ(n*log(n))

(C) θ(n^2)

(D) θ(n^2 log n)

• A

• B

• C

• D

Question 17

Consider the Quicksort algorithm. Suppose there is a procedure for finding a pivot element which splits the list into two sub-lists each of which contains at least one-fifth of the elements. Let T(n) be the number of comparisons required to sort n elements. Then

• T(n) <= 2T(n/5) + n

• T(n) <= T(n/5) + T(4n/5) + n

• T(n) <= 2T(4n/5) + n

• T(n) <= 2T(n/2) + n

Question 18

Let P be a QuickSort Program to sort numbers in ascending order using the first element as pivot. Let t1 and t2 be the number of comparisons made by P for the inputs {1, 2, 3, 4, 5} and {4, 1, 5, 3, 2} respectively. Which one of the following holds?

• t1 = 5

• t1 < t2

• t1 > t2

• t1 = t2

Question 19

You have an array of n elements. Suppose you implement quick sort by always choosing the central element of the array as the pivot. Then the tightest upper bound for the worst case performance is

• O(n²)

• O(n*log(n))

• Theta(n*log(n))

• O(n³)

Question 20

Randomized quicksort is an extension of quicksort where the pivot is chosen randomly. What is the worst case complexity of sorting n numbers using randomized quicksort?

• O(n)

• O(n*log(n))

• O(n²)

• O(n!)