QUICKSORT(ARRAY, left, right)
IF left < right
p = PARTITION(ARRAY, left, right)
QUICKSORT(ARRAY, left, p - 1)
QUICKSORT(ARRAY, p + 1, right)
PARTITION(ARRAY, left, right)
pivot = ARRAY[right];
boundary = left - 1
FOR j = left to right - 1
IF(ARRAY[j] <= pivot)
boundary++
EXCHANGE(ARRAY[boundary] with ARRAY[j])
EXCHANGE(ARRAY[boundary + 1] with ARRAY[right])
return boundary + 1