Possibly related : [ Unordered-MultiMap of Pairs, C++ unordered_map using a custom class type as the key ]
I would like to use a pair of order-less strings as the key for my unordered_map.
For example I would like key1 to be the same as key2
key1 = {"john", "doe"}; key2 = {"doe", "john"};
Maybe I am missing something really silly here.
Here is my test code (doesn't work as I would want it to):
struct Key { std::string first; std::string second; Key(std::string a, std::string b) { first = a; second = b; } bool operator==(const Key k) const { return ((first == k.first && second == k.second) || (first == k.second && second == k.first)); } }; struct KeyHash { std::size_t operator()(const Key& k) const { return std::hash<std::string>()(k.first) ^ (std::hash<std::string>()(k.second) << 1); } }; struct KeyEqual { bool operator()(const Key& lhs, const Key& rhs) const { //return (lhs.first == rhs.first && lhs.second == rhs.second); // not this return ((lhs.first == rhs.first && lhs.second == rhs.second) || (lhs.first == rhs.second && lhs.second == rhs.first)); } }; void test_unorderedMap() { Key s1("John", "Doe"); Key s2("Doe", "John"); Key s3("Mary", "Sue"); Key s4("Sue", "Mary"); // first attempt std::unordered_map<Key, std::string, KeyHash> m1; m1[s1] = "a"; m1[s2] = "b"; m1[s3] = "c"; m1[s4] = "d"; std::cout << "m6[s1] : " << m1.find(s1)->second << std::endl; // prints .. a std::cout << "m6[s2] : " << m1.find(s2)->second << std::endl; // prints .. b std::cout << "m6[s3] : " << m1.find(s3)->second << std::endl; // prints .. c std::cout << "m6[s4] : " << m1.find(s4)->second << std::endl; // prints .. d // second attempt std::unordered_map<Key, std::string, KeyHash, KeyEqual> m2; m2[s1] = "a"; m2[s2] = "b"; m2[s3] = "c"; m2[s4] = "d"; std::cout << "m2[s1] : " << m2.find(s1)->second << std::endl; // prints .. a std::cout << "m2[s2] : " << m2.find(s2)->second << std::endl; // prints .. b std::cout << "m2[s3] : " << m2.find(s3)->second << std::endl; // prints .. c std::cout << "m2[s4] : " << m2.find(s4)->second << std::endl; // prints .. d } 
