std :: map - 如何更改键排序？ [英] std::map - how to change key sorting?

问题描述

我有一个问题， std :: map 。
我正在使用它来映射特定索引下的一些对列表：

I have a problem with std::map. I'm using it to map some list of pairs under a specific index:

map<string, list<pair<string, int> > > List;

它用于Dijkstra算法。
主要问题是地图按字母顺序排序 string 键，如下所示：

It's used in Dijkstra algorithm. The main problem is that map sorts string keys in alphabetical order, like this:

AAA, AA0, AA1, AAB, AC1 = AA0->AA1->AAA->AAB->AC1

但是我想以不同的方式排序：

But I would like to sort it in a different way:

AAA, AA0, AA1, AAB, AC1 = AAA->AAB->AA0->AA1->AC1

有没有解决方法？我读了自己的比较课，但我不知道如何做到这一点。或者可能还有其他一些方法可以解决？

Is there any solution to this? I read about making my own comparing class, but I have no idea how to do this. Or maybe there's some other way to solve it?

推荐答案

你必须提供自己的比较函子，必须通过第3实例化地图时的模板参数。例如：

You have to provide your own comparison functor, which must be passed as 3rd template parameter when instantiating the map. For example:

struct Comp
{
  bool operator()(const std::string& lhs, const std::string& rhs) const
  {
    // implement your comparison logic here
  }
};

这个类的实例是可调用的（因此functor）具有两个字符串参数，并且应该返回true或者基于严格弱订购逻辑的错误。

Instances of this class is callable (hence "functor") with two string parameters, and should return true or false based in a strict weak ordering logic.

然后使用函子类型实例化地图：

Then instantiate the map using the functor type:

std::map<string, list<pair<string, int>>, Comp> List;

现在，地图将使用您的比较逻辑来定义其元素的顺序。

Now the map will use your comparison logic internally to define the ordering of its elements.

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