Quicksort slower than Mergesort?

Question

I was working on implementing a quicksort yesterday, and then I ran it, expecting a faster runtime than the Mergesort (which I had also implemented). I ran the two, and while th

Answer 1

Mergesort is a lot slower for random array based data, as long as it fits in ram. This is the first time I see it debated.

• qsort the shortest subarray first.
• switch to insertion sort below 5-25 elements
• do a normal pivot selection

Your qsort is very slow because it tries to partition and qsort arrays of length 2 and 3.