Consider the Quicksort algorithm. Suppose there is a procedure for fin...
For the case where n/5 elements are in one subset, T(n/5) comparisons are needed for the first subset with n/5 elements, T(4n/5) is for the rest 4n/5 elements, and n is for finding the pivot.
If there are more than n/5 elements in one set then other set will have less than 4n/5 elements and time complexity will be less than T(n/5) + T(4n/5) + n because recursion tree will be more balanced.
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Consider the Quicksort algorithm. Suppose there is a procedure for fin...
Explanation:
The given question is related to the Quicksort algorithm and asks for the relation between the number of comparisons required to sort n elements (T(n)) and the pivot element selection strategy. Let's analyze the options one by one.
Option A: T(n) = 2T(n/5)
This option suggests that the number of comparisons required to sort n elements is twice the number of comparisons required to sort n/5 elements. However, this contradicts the given condition that the pivot element splits the list into two sub-lists, each containing at least one-fifth of the elements. Hence, this option is incorrect.
Option B: T(n) = T(n/5) * T(4n/5)
This option suggests that the number of comparisons required to sort n elements is equal to the number of comparisons required to sort n/5 elements multiplied by the number of comparisons required to sort 4n/5 elements. This option satisfies the given condition that the pivot element splits the list into two sub-lists, each containing at least one-fifth of the elements. Therefore, this option is correct.
Option C: T(n) = 2T(4n/5)
This option suggests that the number of comparisons required to sort n elements is twice the number of comparisons required to sort 4n/5 elements. However, this contradicts the given condition that the pivot element splits the list into two sub-lists, each containing at least one-fifth of the elements. Hence, this option is incorrect.
Option D: T(n) = 2T(n/2) * n
This option suggests that the number of comparisons required to sort n elements is twice the number of comparisons required to sort n/2 elements multiplied by n. This option does not consider the condition of the pivot element splitting the list into two sub-lists, each containing at least one-fifth of the elements. Hence, this option is incorrect.
Therefore, the correct answer is Option B: T(n) = T(n/5) * T(4n/5) as it satisfies the given condition of the pivot element selection strategy.