Unordered associative containers (C++): Difference between revisions

Revision as of 18:46, 8 March 2016

Revision as of 12:00, 11 June 2016

Line 202:

To use custom objects in std::unordered_map, a custom hash function must be defined. This function takes a const reference to the custom type and returns a size_t

<source lang="cpp">

#include <unordered_map>

struct X{int i,j,k;};

struct hash_X{

size_t operator()(const X &x) const{

return std::hash<int>()(x.i) ^ std::hash<int>()(x.j) ^ std::hash<int>()(x.k);

}

};