如何在C ++中创建无序的整数对？ [英] How to make unordered set of pairs of integers in C++?

问题描述

程序不编译无序的整数对，而是整数。可以在用户定义的类型上使用unordered_set及其成员函数，以及如何定义它？

The program does not compile an unordered set of pairs of integers, but it does for integers. Can unordered_set and its member functions be used on user defined types, and how can I define it?

#include <unordered_set>
...

class A{
...
private: 
std::unordered_set< std::pair<int, int> > u_edge_;
};

error: no matching function for call to 'std::unordered_set<std::pair<unsigned int, unsigned int> >::unordered_set()'

推荐答案

在VS2010 SP1（VC10），但它无法编译与GCC g ++ 4.7.2。

Your code compiles on VS2010 SP1 (VC10), but it fails to compile with GCC g++ 4.7.2.

但是，你可能要考虑 boost ::哈希从 Boost.Functional 哈希 std :: pair （此外，您的代码也使用g ++编译）。

However, you may want to consider boost::hash from Boost.Functional to hash a std::pair (with this addition, your code compiles also with g++).

#include <unordered_set>
#include <boost/functional/hash.hpp>

class A
{
private: 
    std::unordered_set< 
        std::pair<int, int>, 
        boost::hash< std::pair<int, int> > 
    > u_edge_;
};

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