Non-recursive quicksort

[LarryChen]

Can any guru here give me a working C example for non-recursive quicksort? Actually there is a non-recursive quicksort example from the book "Algorithms in C" by Robert Sedgewick. Here is the code,

int top = -1;

struct s
{
	int a;
	int b;	
}stack[100];

void push(int x, int y)
{
	top++;
	stack[top].a = x;
	stack[top].b = y;
}

void pop(int& x, int& y)
{
	x = stack[top].a;
	y = stack[top].b;
	top--;
}


int partition(int a[], int l, int r)
{
	int i = l-1;
	int j = r;
	int v = a[r];

	for(;;)
	{
		while(a[++i] < v);
		while(a[--j] > v  && j>l && j > i);

		if(j<=l || j<=i)
			break;
	
		swap(a[i], a[j]);
	}
	swap(a[i], a[r]);
	return i;
}

void quicksort(int a[], int l, int r)
{
	int i;

	push(r, l);
	while(top!=-1)
	{
		pop(l, r);
		if(r <= l)
			continue;

		i = partition(a, l, r);

		if(i-l > r-i)
		{
			push(l, i-1);
			push(i+1, r);
		}
		else
		{
			push(i+1, r);
			push(l, i-1);
		}		
	}	
}

But it doesn't work. Any improvement to make it work? Thanks so much!

[Zachm]

Haven't really had a look on the code you posted, but maybe have a look here ?

Regards,
Zachm

[LarryChen]

Thanks for the link. I think it is a good one.

Haven't really had a look on the code you posted, but maybe have a look here ?

Regards,
Zachm