def __update_interval(self, q_left, q_right, val, index, left, right):
    
    if left >= q_left and right <= q_right:     # 节点所在区间被 [q_left, q_right] 所覆盖
        interval_size = (right - left + 1)      # 当前节点所在区间大小
        self.tree[index].val = interval_size * val # 当前节点所在区间每个元素值改为 val
        self.tree[index].lazy_tag = val         # 将当前节点的延迟标记为区间值
        return
    if right < q_left or left > q_right:        # 节点所在区间与 [q_left, q_right] 无关
        return 0