STL优先级队列 - 删除项目 [英] STL Priority Queue - deleting an item

问题描述

我想使用C ++ STL priority_queue 容器适配器来实现计时器排队系统。

I want to implement a timer queuing system using the C++ STL priority_queue container adapter.

我的问题是，我想偶尔取消一个计时器，但没有接口，使我能够轻松地删除在priority_queue不是顶部项目的项目。

My problem is that I want to occasionally cancel a timer, however there are no interfaces that enable me to easily delete an item in the priority_queue that is not the top item.

有任何建议吗？

感谢您的协助。

推荐答案

我有一个完全相同的场景，并执行以下操作：

I had the exact same scenario once and did the following:

• 我保存在 std :: priority_queue 中的结构仅包含排序时间和 std的索引:: vector< Handler> （在我的情况下 Handler 是 boost :: function 但也可以是指向接口或函数的指针）


• 当添加一个计时器时，我会在处理程序 ¹ 的向量中找到一个空索引，处理程序。将索引和时间存储在priority_queue中。将索引返回给客户端作为令牌取消


• 取消计时器，传递添加时接收到的索引。清除该索引处的处理程序（对于 boost :: function 调用 clear（），如果使用指针，当它是回调定时器时，从优先级队列获得它的处理程序索引并检查处理程序向量 - 如果在那个位置的处理程序是空的（）/ NULL，定时器已取消。将处理程序索引标记为自由 ² 。

• the structure I kept in std::priority_queue contained only the time to sort by and an index to a std::vector<Handler> (in my case Handler was boost::function, but could as well be pointer to interface or function)
• when adding a timer, I'd find a free index in the vector of handlers¹ and store the handler at that index. Store the index and the time in the priority_queue. Return the index to the client as token to cancel
• to cancel a timer, pass the index received when adding it. Clear the handler at that index (for boost::function call clear(), if using pointers, set it to zero)
• when it's time to callback a timer, get its handler index from the priority queue and check the handlers vector - if the handler at that position is empty()/NULL, the timer has been canceled. Mark that handler index as free².

¹ 为了快速找到自由索引，我使用了一个单独的 std :: stack 的索引。当添加一个定时器并且栈是空的，在向量的末尾添加;

¹ To make finding a free index fast, I used a separate std::stack of indices. When adding a timer and that stack is empty, add at the end of vector; otherwise pop the top index and use it.

² 这是将索引推送到自由索引堆栈的点。

² Here's the point when you push the index to the free indices stack

整个事情有点棘手和容易出错，特别是如果你的定时器回调需要添加或取消定时器。 以上是我取消计时器类的链接，此代码为公共域

The whole thing is somewhat tricky and error-prone, especially if your timer callbacks need to add or cancel timers. Here's a link to my canceling timer class described above, this code is public domain

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