Using the partition, the first pivot is using the a[right] or a[left+(right-left)/2]. For the latter, remember to swap the a[left+(right-left)/2] to the a[right] firstly.
Then
void quicksort(int* array, int left, int right)
{
if (right > left) // subarray of 0 or 1 elements already sorted
{
//select a pivotIndex in the range left ≤ pivotIndex ≤ right
// see Choice of pivot for possible choices
// see Choice of pivot for possible choices
int pivotIndex = left+(right-left)/2;
int pivotNewIndex = inplace_partition(array, left, right,pivotIndex); // element at pivotNewIndex is now at its final position
quicksort(array, left, pivotNewIndex - 1); // recursively sort elements on the left of pivotNewIndex
quicksort(array, pivotNewIndex + 1, right); // recursively sort elements on the right of pivotNewIndex
}
}
One interesting thing for swap:
Can you see any problem for such code looking wise?
void swap(int& a, int& b)
{
a = a + b;
b = a - b;
a = a - b;
}
Reference: Introduction to Algorithms, Chapter 7.1.
