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# Data Structure MCQ - Sorting

This section focuses on the "Sorting" of the Data Structure. These Multiple Choice Questions (mcq) should be practiced to improve the Data Structure skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

1. What is recurrence for worst case of QuickSort and what is the time complexity in Worst case?

A. Recurrence is T(n) = T(n-2) + O(n) and time complexity is O(n^2)
B. Recurrence is T(n) = T(n-1) + O(n) and time complexity is O(n^2)
C. Recurrence is T(n) = 2T(n/2) + O(n) and time complexity is O(nLogn)
D. Recurrence is T(n) = T(n/10) + T(9n/10) + O(n) and time complexity is O(nLogn)

2. Which of the following is not a stable sorting algorithm?

A. Insertion sort
B. Selection sort
C. Bubble sort
D. Merge sort

3. What is an external sorting algorithm?

A. Algorithm that uses tape or disk during the sort
B. Algorithm that uses main memory during the sort
C. Algorithm that involves swapping
D. Algorithm that are considered ‘in place’

4. If the number of records to be sorted is small, then …… sorting can be efficient.

A. Merge
B. Heap
C. Selection
D. Bubble

5.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.

A. O(n^2 Logn)
B. O(n^2)
C. O(n Logn Logn)
D. O(nLogn)

6. Which of the following is not an in-place sorting algorithm?

A. Selection sort
B. Heap sort
C. Quick sort
D. Merge sort

7. What is the advantage of bubble sort over other sorting techniques?

A. It is faster
B. Consumes less memory
C. Detects whether the input is already sorted
D. All of the mentioned

8.The complexity of sorting algorithm measures the …… as a function of the number n of items to be sorter.

A. average time
B. running time
C. average-case complexity
D. case-complexity

9. Suppose we are sorting an array of eight integers using quicksort, and we have just finished the first partitioning with the array looking like this:
2 5 1 7 9 12 11 10
Which statement is correct?

A. The pivot could be either the 7 or the 9.
B. The pivot could be the 7, but it is not the 9
C. The pivot is not the 7, but it could be the 9
D. Neither the 7 nor the 9 is the pivot.

10.Consider the situation in which assignment operation is very costly. Which of the following sorting algorithm should be performed so that the number of assignment operations is minimized in general?

A. Insertion sort
B. Selection sort
C. Heap sort
D. None

11. In the following scenarios, when will you use selection sort?

A. The input is already sorted
B. A large file has to be sorted
C. Large values need to be sorted with small keys
D. Small values need to be sorted with large keys

12. What is the worst case complexity of selection sort?

A. O(nlogn)
B. O(logn)
C. O(n)
D. O(n2)

13. What is the advantage of selection sort over other sorting techniques?

a) It requires no additional storage space
b) It is scalable
c) It works best for inputs which are already sorted
d) It is faster than any other sorting technique

14. What is the average case complexity of selection sort?

A. O(nlogn)
B. O(logn)
C. O(n)
D. O(n2)

15. What is the disadvantage of selection sort?

A. It requires auxiliary memory
B. It is not scalable
C. It can be used for small keys
D. None of the mentioned

16. The given array is arr = {3,4,5,2,1}. The number of iterations in bubble sort and selection sort respectively are,

A. 5 and 4
B. 4 and 5
C. 2 and 4
D. 2 and 5

17. The given array is arr = {1,2,3,4,5}. (bubble sort is implemented with a flag variable)The number of iterations in selection sort and bubble sort respectively are,

A. 5 and 4
B. 1 and 4
C. 0 and 4
D. 4 and 1

18.What is the best case complexity of selection sort?

A. O(nlogn)
B. O(logn)
C. O(n)
D. O(n2)

19. What is an internal sorting algorithm?

A. Algorithm that uses tape or disk during the sort
B. Algorithm that uses main memory during the sort
C. Algorithm that involves swapping
D. Algorithm that are considered ‘in place’

20.What is the worst case complexity of bubble sort?

A. O(nlogn)
B. O(logn)
C. O(n)
D. O(n2)

21. What is the average case complexity of bubble sort?

A. O(nlogn)
B. O(logn)
C. O(n)
D. O(n2)

22. The given array is arr = {1,2,4,3}. Bubble sort is used to sort the array elements. How many iterations will be done to sort the array?

A. 4
B. 2
C. 1
D. 0

23.What is the best case efficiency of bubble sort in the improvised version?

A. O(nlogn)
B. O(logn)
C. O(n)
D. O(n2)

24. QuickSort can be categorized into which of the following?

A. Brute Force technique
B. Divide and conquer
C. Greedy algorithm
D. Dynamic programming

25. What is a randomized QuickSort?

A. The leftmost element is chosen as the pivot
B. The rightmost element is chosen as the pivot
C. Any element in the array is chosen as the pivot
D. A random number is generated which is used as the pivot

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