GATE | GATE CS 2019 | Question 30

An array of 25 distinct elements is to be sorted using quicksort. Assume that the pivot element is chosen uniformly at random. The probability that the pivot element gets placed in the worst possible location in the first round of partitioning (rounded off to 2 decimal places) is _________.

Note: This was Numerical Type question.
(A) 0.08
(B) 0.0016
(C) 0.04
(D) 0.0008

Answer: (A)

Explanation: Given an array of 25 distinct elements, and pivot element is chosen uniformly randomly. So, there are only 2 worst case position in the pivot element is either first (or) last.

Therefore, required probability is,

= 2/25
= 0.08

So, option (A) is correct.

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