# include <iostream.h>

# include "vector.h"
# include "vector.c"

extern void swap(vector<int> &, int, int);

int prtition(vector<int> & v, int low, int high, int pivotIndex)
{
	// move the pivot value to the bottom of the vector
	if (pivotIndex != low) 
		swap(v, low, pivotIndex);
	pivotIndex = low;
	low++;

	// invarient:
	//	v[i] for i less than low are less than or equal to pivot
	//	v[i] for i greater than high are greater than pivot

	// move elements into place
	while (low <= high) {
		if (v[low] <= v[pivotIndex])
			low++;
		else if (v[high] > v[pivotIndex])
			high--;
		else
			swap(v, low, high);
		}

	// put pivot back between two groups
	if (high != pivotIndex)
		swap(v, pivotIndex, high);
	return high;
}

void qackSort(vector<int> & v, int low, int high)
{
	for (int ii = 0; ii < 10; ii++)
		cout << v[ii] << " ";
	cout << " & sorting " << low << " to " << high;

	// no need to sort a vector of zero or one elements
	if (low >= high) {
		cout << "\\\\\n";
		return;
		}

	// select the pivot value
	int pivotIndex = (low + high) / 2;
	cout << " pivot index is " << pivotIndex << "\\\\\n";

	// partition the vector
	pivotIndex = prtition(v, low, high, pivotIndex);

	for (ii = 0; ii < 10; ii++)
		cout << v[ii] << " ";
	cout << " & after partition \\\\\n";


	// sort the two sub arrays
	if (low < pivotIndex)
		qackSort(v, low, pivotIndex - 1);
	if (pivotIndex < high)
		qackSort(v, pivotIndex + 1, high);
}

vector<int> vals(10);

//----------------------------------------------------------------------

main() {
	vals[0] = 8;
	vals[1] = 2;
	vals[2] = 6;
	vals[3] = 4;
	vals[4] = 0;
	vals[5] = 1;
	vals[6] = 3;
	vals[7] = 5;
	vals[8] = 7;
	vals[9] = 9;

	qackSort(vals, 0, 9);
}