void levelorder(TREE t)
{
	TREE st[20];
	int i=0,k;
	st[i++]=t;
	for(k=0;st[k]!=NULL;k++)
	{
	cout<<st[k]->i;
	st[i++]=st[k]->lt;
	st[i++]=st[k]->rt;
	}
}

The for loop will stop when it encounters a first node NULL in level order traversal.. 
this will not actually detect complete.. but almost complete will be detected..