Which one of the following is the recurrence equation for the worst ca...
In worst case, the chosen pivot is always placed at a corner position and recursive call is made for following. a) for subarray on left of pivot which is of size n-1 in worst case. b) for subarray on right of pivot which is of size 0 in worst case.
View all questions of this test
Which one of the following is the recurrence equation for the worst ca...
Understanding Quicksort Time Complexity
Quicksort is a popular sorting algorithm that employs a divide-and-conquer strategy. To analyze its worst-case time complexity, we must understand how it breaks down the problem.
Recurrence Relation Explanation
In the worst case, Quicksort can degenerate into a situation where it consistently picks the smallest or largest element as the pivot. This results in unbalanced partitions. The recurrence relation that best describes this scenario is:
- T(n) = T(n - 1) + T(0) + cn
Here’s a breakdown of this relation:
- T(n - 1): This part represents the recursive call to sort the remaining elements. In the worst case, one subproblem will have n-1 elements, and the other will have 0.
- T(0): This represents the base case where no elements are left to sort, which contributes a constant time.
- cn: This term accounts for the time taken to partition the array around the pivot, which requires linear time.
Why Other Options Are Incorrect
- Option A (T(n) = 2T(n/2) + cn): This represents a balanced partitioning scenario, typical of the average case, not the worst case.
- Option C (T(n) = 2T(n - 2) + cn): This would imply that two nearly equal partitions are created, which is not the case in the worst scenario.
- Option D (T(n) = T(n/2) + cn): This suggests that only one recursive call happens, which is incorrect for the worst case.
Conclusion
Thus, the correct recurrence relation for the worst-case time complexity of the Quicksort algorithm is indeed T(n) = T(n - 1) + T(0) + cn, making option B the right choice.