Searching, Sorting and Big O - Java: How to Program Early Objects - page 838

12 2 6 4 89 8 10 37 68 45
Element 12 is in italics to indicate that it was just swapped with 37 .
Starting from the left of the array, but beginning with the element after 12, com-
pare each element with 37 until an element greater than 37 is found—then swap 37
and that element. The first element greater than 37 is 89, so 37 and 89 are swapped.
The new array is
12 2 6 4 37 8 10 89 68 45
Starting from the right, but beginning with the element before 89, compare each ele-
ment with 37 until an element less than 37 is found—then swap 37 and that element.
The first element less than 37 is 10, so 37 and 10 are swapped. The new array is
12 2 6 4 10 8 37 89 68 45
Starting from the left, but beginning with the element after 10, compare each element
with 37 until an element greater than 37 is found—then swap 37 and that element.
There are no more elements greater than 37 , so when we compare 37 with itself, we
know that 37 has been placed in its final location in the sorted array. Every value to the
left of 37 is smaller than it, and every value to the right of 37 is larger than it.
Once the partition has been applied on the previous array, there are two unsorted
subarrays. The subarray with values less than 37 contains 12, 2, 6, 4, 10 and 8. The
subarray with values greater than 37 contains 89, 68 and 45. The sort continues recur-
sively, with both subarrays being partitioned in the same manner as the original array.
Based on the preceding discussion, write recursive method quickSortHelper to
sort a one-dimensional integer array. The method should receive as arguments a start-
ing index and an ending index on the original array being sorted.