Efficiency of Sort Algorithms

Question

I am studying up for a pretty important interview tomorrow and there is one thing that I have a great deal of trouble with: Sorting algorithms and BigO efficiencies.

What number is important to know? The best, worst, or average efficiency?

Answer 1

worst, followed by average. be aware of the real-world impact of the so-called "hidden constants" too - for instance, the classic quicksort algorithm is O(n^2) in the worst case, and O(n log n) on average, whereas mergesort is O(n log n) in the worst case, but quicksort will outperform mergesort in practice.