Show that the running time of
QUICKSORTis $\Theta(n^2)$ when the array $A$ contains distict elements and is sorted in decreasing order.
In this case
PARTITION always returns $p$ because all the elements are
greater than the pivot. While the if will never be executed, we still get
one empty partition and the recurrence is $T(n) = T(n-1) + \Theta(n)$ (even if
its body is not executed, the for is still $\Theta(n)$).