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

问题描述

我有一个问题与 std :: map 。
我使用它来映射在特定索引下的一些对的列表：

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。
主要的问题是map按字母顺序排序 string 键，例如：

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

但我想用不同的方式排序：

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

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

有没有任何解决方案？我读了关于做自己的比较课，但我不知道如何做到这一点。

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，它必须作为3rd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（因此是functor），有两个字符串参数，或基于严格弱排序逻辑的错误。

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;

现在地图将在内部使用您的比较逻辑来定义其元素的排序。

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

这篇关于std :: map - 如何更改键排序？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！