什么是使用两个键与std :: map的最好的方法？ [英] What is the best way to use two keys with a std::map?

问题描述

我有一个std :: map，我用来存储x& y坐标。我的数据非常稀疏，所以我不想使用数组或向量，这将导致大量的内存浪费。我的数据范围从-250000到250000，但我最多只有几千点。

I have a std::map that I'm using to store values for x & y coordinates. My data is very sparse, so I don't want to use arrays or vectors, which would result in a massive waste of memory. My data ranges from -250000 to 250000 but I'll only have a few thousand points at the most.

目前我创建一个带有两个坐标（即12x45）的std :: string并将其作为键。这似乎不是最好的方法。

Currently I'm creating a std::string with the two coordinates (ie "12x45") and using it as a key. This doesn't seem like the best way to do it.

我的其他想法是使用一个int64，并把两个int32s，并使用它作为一个键。

My other thoughts were to use an int64 and shove the two int32s into it and use it as a key.

或使用具有两个坐标的类。对用作键的类有什么要求？

Or to use a class with the two coordinates. What are the requirements on a class that is to be used as the key?

这是什么最好的方法？

What is the best way to do this? I'd rather not use a map of maps.

推荐答案

使用std :: pair< int32，int32>

Use std::pair<int32,int32> for the key:

std::map<std::pair<int,int>, int> myMap;

myMap[std::make_pair(10,20)] = 25;
std::cout << myMap[std::make_pair(10,20)] << std::endl;

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