1 if p < r
2 q = PARTITION(A,p,r)
3 QUICKSORT(A, p , q-1)
4 QUICKSORT(A, q + 1, r)
How would you modify QUICKSORT to sort into nonincreasing order?
If you observe PARTITION of the array algorithm carefully then you'll observe at line 4 i.e. in
$if A[j]\leq x$
simply the change it to $\leqslant$ which is
$if A[j]\geqslant x$
this will make all the elements greater than pivot move to the left of the array and rest to the right which is the desired result.