Question

Please answer only if you are sure and make it clear to understand. Do not make it too long and complicated. Thank you in advance.

"Give an example of showing that quicksort is not a stable sorting algorithm".

Answer 1

When we consider example as key value pairs like (3, 1),(2,1), (2,2), (5,2) and sort on the basis of x, we can see that the quicksort doesn't maintain the order of (2,1) and (2,2).

Output by quicksort : (2,2), (2,1), (3,1), (5,2)

Stable algorithm : (2,1), (2,2), (3,1), (5,2)