Top MCQs on SelectionSort Algorithm with Answers

Question 1

Consider a situation where swap operation is very costly. Which of the following sorting algorithms should be preferred so that the number of swap operations are minimized in general?

• A. Heap Sort
• B. Selection Sort
• C. Insertion Sort
• D. Merge Sort

Answer: (B)

Selection sort makes O(n) swaps which is the minimum among all sorting algorithms mentioned above.

Hence Option(B) is the correct answer.

Question 2

Which sorting algorithm will take least time when all elements of input array are identical? Consider typical implementations of sorting algorithms.

• A. Insertion Sort
• B. Heap Sort
• C. Merge Sort
• D. Selection Sort

Answer: (A)

The insertion sort will O(n) time when input array is already sorted.

Question 3

Which of the following sorting algorithms has the lowest worst-case complexity?

• A. Merge Sort
• B. Bubble Sort
• C. Quick Sort
• D. Selection Sort

Answer: (A)

Worst-case complexities for the above sorting algorithms are as follows:

• Merge Sort: O(n*log(n))
• Bubble Sort: O(n²)
• Quick Sort: O(n²)
• Selection Sort: O(n²)

Question 4

Which is the correct order of the following algorithms with respect to their time Complexity in the best case ?

• A. Merge sort > Quick sort >Insertion sort > selection sort
• B. insertion sort < Quick sort < Merge sort < selection sort
• C. Merge sort > selection sort > quick sort > insertion sort
• D. Merge sort > Quick sort > selection sort > insertion sort

Answer: (B)

In best case, 

Quick sort: O (nlogn) 
Merge sort: O (nlogn)
Insertion sort: O (n)
Selection sort: O (n^2)  

Question 5

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

• A. Insertion Sort
• B. Quick Sort
• C. Heap Sort
• D. Selection Sort

Answer: (D)

Selection Sort is an in-place algorithm having minimum number of swaps. It works on greedy approach and takes O(n) swaps to sort the array of n elements. Refer: GATE-CS-2006 | Question 14

Question 6

How many comparisons are needed to sort an array of length 5 if a straight selection sort is used and array is already in the opposite order?

• A. 1
• B. 5
• C. 10
• D. 20

Answer: (C)

Consider the array: 5 4 3 2 1 1st iteration will compare 4 numbers with the 5 2nd iteration will compare 3 numbers with the 4 3rd iteration will compare 2 numbers with the 3 4th iteration i will compare 1 number with the 2 So, the total number of comparisons is 4 + 3 + 2 + 1 = 10 It can be viewed as the sum of the sequence of the first (n-1) numbers starting by 1 S = ((1 + (n-1) )*(n-1) )/2 S = 10 Option (C) is correct.