Algorithms · Question 8 · Medium
Quick sort always picks the last element as the pivot. For which input does it show its worst-case O(n²) behaviour?
- An array that is already sorted
- An array of random distinct values
- An array whose elements are all distinct primes
- An array of size that is a power of 2
Answer and explanation
Answer: A. An array that is already sorted
Explanation: On a sorted array the last element is the maximum, so each partition leaves n - 1 elements on one side and none on the other, giving n + (n - 1) + ... = O(n²) comparisons.
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