QuickSort Problem !!

[fourkawhell]

I don't know why the recursion QuickSort isn't execute.

   #include<iostream>

using namespace std;

void input(int *a, int n)
{
	for (int i = 0; i < n; i++)
	{
		cout << "a[" << i << "]= ";
		cin >> a[i];
	}
}

void output(int *a, int n)
{
	for (int i = 0; i < n; i++)
	{
		cout << a[i] << " ";
	}
}

int QuickSort(int *a, int left, int right)
{
	int oldright = right;
	int pivot = left;
	while (left < right)
	{
		while (a[right] >= a[pivot])
		{
			right = right - 1;
		}
		if (a[right] < a[pivot] && right > pivot)
		{
			swap(a[right], a[pivot]);
			pivot = right;

		}
		while (a[left] <= a[pivot])
		{
			left = left + 1;
		}
		if (a[left] > a[pivot] && left < pivot)
		{
			swap(a[left], a[pivot]);
			pivot = left;
		}
	}
	QuickSort(a, 0, pivot - 1);
	QuickSort(a, pivot + 1, oldright);
	return 0;
}

int main()
{
	int n;
	cout << "Enter The Length of Array: "; cin >> n;
	int *a = new int[n];
	input(a, n);
	QuickSort(a, 0, n - 1);
	output(a, n);
	return 0;
}

[anup30]

you have not written the partition function.
http://mathbits.com/MathBits/CompSci/Arrays/Quick.htm

// quick sort // descending
#include <iostream>
using namespace std;

int partition(int ar[], int top, int bottom)  // simpler version of above link
{
	int i = top;
	int j = bottom;
		
	while (i < j)
	{
		while (ar[top] > ar[j])
	 		j--;

		while (ar[top] < ar[i])
			i++;

		if (i < j) 
			std::swap(ar[i],ar[j]);  // swap		
	} 
	return j;   // returns pivot subscript
}


void QuickSort(int arr[], int top, int bottom)
{
	// top = subscript of beginning of array
	// bottom = subscript of end of array	
	if (top < bottom)
	{
		int middle = partition(arr, top, bottom);  // middle = pivot
		QuickSort(arr, top, middle);   // sort first section
		QuickSort(arr, middle+1, bottom);    // sort second section
	}
	return;
}

int main()
{
	int ar[] = {2,9,1,3,5,7,8,6,4,0};
	int SIZE = 10;
	cout << "Input: ";
	for ( int i = 0; i < SIZE; i++ )
		cout << ar[i] << " ";
	cout << "\n\n";   

	QuickSort(ar, 0, SIZE-1);

    cout << "Output: ";
	for ( int i = 0; i < SIZE; i++ )
		cout << ar[i] << " ";
	cout << "\n\n";
    
return 0;
}

EDIT:
you can also write the partition function as wikipedia:
http://en.wikipedia.org/wiki/Quicksort