自底向上归并，链表

link merge_sort(link t)
{
	queue<link> que;
	if (0 == t || 0 == t->p_next) return t;

	for (link u = 0; t!=0; t=u)
	{
		u = t->p_next;
		t->p_next = 0;
		que.push(t);
	}
	t = que.front();que.pop();
	while (!que.empty()) // is flexiable
	{
		que.push(t);
		link a = que.front();que.pop();
		link b = que.front();que.pop();
		t = merge_list(a, b);
	}
	return t;

}