QUICKSORT(A, p, r)
1 if p < r
2   then q = PARTITION(A, p, r)
3 QUICKSORT(A, p, q)
4 QUICKSORT(A, q + 1, r)

PARTITION(A, p, r)
1 x = A[p]
2 i = p − 1
3 j = r + 1
4 while TRUE
5   do repeat j = j − 1
6     until A[j] ≤ x
7   do repeat i = i + 1
8     until A[i] ≥ x
9 if i < j
10   then exchange values A[i] and A[j]
11 else return j