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Consider the Quicksort algorithm. Suppose there is a procedure for finding a pivot element which splits the list into two sub-lists each of which contains at least one-fifth of the elements. Let T(n) be the number of comparisons required to sort n elements. Then
  • a)
    T(n) <= 2T(n/5) + n
  • b)
    T(n) <= T(n/5) + T(4n/5) + n
  • c)
    T(n) <= 2T(4n/5) + n
  • d)
    T(n) <= 2T(n/2) + n
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
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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Most Upvoted Answer
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.
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Consider the Quicksort algorithm. Suppose there is a procedure for finding a pivot element which splits the list into two sub-lists each of which contains at least one-fifth of the elements. Let T(n) be the number of comparisons required to sort n elements. Thena)T(n) <= 2T(n/5) + nb)T(n) <= T(n/5) + T(4n/5) + nc)T(n) <= 2T(4n/5) + nd)T(n) <= 2T(n/2) + nCorrect answer is option 'B'. Can you explain this answer?
Question Description
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