heapsort

#define PARENT(__i) (__i / 2)
#define LEFT(__i) (__i * 2)
#define RIGHT(__i) (__i * 2 + 1)

int heap_size,length;

/*inline*/void exchange(int *a,int *b)
{
	*a ^= *b;
	*b = *a ^ *b;
	*a ^= *b;
	return;
}

void max_heapify(int A[],int i)
{
	int l,r;
	int largest;

	l = LEFT(i);
	r = RIGHT(i);
	largest = (l <= heap_size && A[l] > A[i])? l: i;
	if(r <= heap_size && A[r] > A[largest])
		largest = r;
	if(largest != i) {
		exchange(&A[i],&A[largest]);
		max_heapify(A,largest);
	}
	return;
}

void build_max_heap(int A[])
{
	int i;

	heap_size = length;
	for(i = length / 2;i > 0;i--)
		max_heapify(A,i);
	return;
}

void heapsort(int A[])
{
	int i;

	build_max_heap(A);
	for(i = length;i > 1;i--) {
		exchange(&A[1],&A[i]);
		heap_size--;
		max_heapify(A,1);
	}
	return;
}