I did not understand this

#1

i did not understand this.
i did not understand this.

#2

Paste the question here.

#3

Q2. Quick Sort

Which of the following changes to typical QuickSort improves its performance on average and are generally done in practice?

  1. Randomly picking up to make worst case less likely to occur.
  2. Calling insertion sort for small sized arrays to reduce recursive calls.
  3. QuickSort is tail recursive, so tail call optimizations can be done.
  4. A linear time median searching algorithm is used to pick the median, so that the worst case time reduces to O(n Log n)

1 and 2

2, 3 and 4

1, 2 and 3

2, 3 and 4

#4

https://gateoverflow.in/13321/following-quicksort-improves-performance-generally-practice

Refer these links.

#5

I already googled before asking this question.
i did not understand properly from both the above links.

#6

It is a completely theoretical question. You have to read all the materials there to understand it completely. Just google the terms which you cannot understand.

You know from the lecture that we use Randomized quick sort as its worst case complexity is O(nlogn) whereas the normal quick sort has a worst case complexity of O(n^2).So 1st option will surely be an answer.
Option 3 is also correct. You can read it from here https://www.geeksforgeeks.org/tail-recursion/
Option 2 is correct and is used in Hybrid Quicksort algorithm. You can read about its theory from here https://www.techiedelight.com/hybrid-quicksort/

Last option is incorrect as finding a median is O(n) operation. In quick sort, for each subarray, you will have to find the median so the worst case of the sorting will be O(n^2)

Please read the articles in the link to understand clearly.