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You have an array of n elements. Suppose you implement quicksort by always choosing the central element of the array as the pivot. Then the tightest upper bound for the worst case performance is

1. O(n²)
2. O(n log n)
3. Θ(n log n)
4. O(n³)

Correct answer: O(n²)

Solution

Choosing the central element as the pivot in quicksort can lead to unbalanced partitions, especially if the array is already sorted or nearly sorted, resulting in a worst-case scenario where the algorithm behaves like selection sort, thus having a time complexity of O(n²).

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