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國立中央大學 2026 · 考試 · 第 44 題

Given the following pseudo code of Quicksort algorithm, which of the following statement is the least accurate?

 1  Quicksort(A,p,r)
 2      if p<r
 3          q=Partition(A,p,r)
 4          Quicksort(A,p,q-1)
 5          Quicksort(A,q+1,r)
 6
 7  Partition(A,p,r)
 8      x=A[r]
 9      i=p-1
10      for j=p to r-1
11          if A[j]<=x
12              i=i+1
13              exchange A[i] with A[j]
14      exchange A[i+1] with A[r]
15      return i+1

(A)
It is stable.
(B)
It is in-place.
(C)
Its worst time performance is O(n²).
(D)
The output of Quicksort() is a non-decreasing sorted sequence.
(E)
The variable x is usually called the pivot.

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