O'z sinfingizni map yoki unordered_map ichida kalit sifatida ishlatish uchun nima qilish kerak?

std::map uchun:

Sizning sinfingiz uchun < taqqoslash operatorini aniqlash kerak.

#include <map>
#include <string>

struct MyKey {
    int id;
    std::string name;

    // "<" operatorini aniqlaymiz
    bool operator<(const MyKey& other) const {
        if (id != other.id) {
            return id < other.id;
        }
        return name < other.name;
    }
};

int main() {
    std::map<MyKey, int> myMap;
    MyKey key1{1, "apple"};
    MyKey key2{2, "banana"};
    myMap[key1] = 10;
    myMap[key2] = 20;
    return 0;
}

std::unordered_map uchun:

Sizning sinfingiz uchun hash funksiyasini (hasher) aniqlash va, agar kerak bo'lsa, == tenglik operatorini ham belgilash kerak. Standart std::hash tipi uchun maxsus hash funksiyasi mavjud emas.

Hash funksiyasini aniqlash usullari:

1. std nom space ichida std::hashni ortiqcha yuklash (maslahat berilmaydi):

   #include <unordered_map>
   #include <string>
   #include <functional> // std::hash uchun
   
   struct MyKey {
       int id;
       std::string name;
   
       // "==" operatorini aniqlaymiz
       bool operator==(const MyKey& other) const {
           return id == other.id && name == other.name;
       }
   };
   
   // MyKey uchun std::hash'ni maxsuslashtirish
   namespace std {
       template <>
       struct hash<MyKey> {
           size_t operator()(const MyKey& key) const {
               // Oddiy hashlarni birlashtirish misoli
               // Murakkab va mustahkam hash funksiyalari afzalroq bo'lishi mumkin
               return hash<int>()(key.id) ^ (hash<std::string>()(key.name) << 1);
           }
       };
   }
   
   int main() {
       std::unordered_map<MyKey, int> myUnorderedMap;
       MyKey key1{1, "apple"};
       MyKey key2{2, "banana"};
       myUnorderedMap[key1] = 10;
       myUnorderedMap[key2] = 20;
       return 0;
   }
   

2. Hash funksiyasini shablon parametr sifatida o'tkazish:

   #include <unordered_map>
   #include <string>
   #include <functional>
   
   struct MyKey {
       int id;
       std::string name;
   
       // "==" operatorini aniqlaymiz
       bool operator==(const MyKey& other) const {
           return id == other.id && name == other.name;
       }
   };
   
   // Hash strukturasini aniqlash
   struct MyKeyHash {
       size_t operator()(const MyKey& key) const {
           return std::hash<int>()(key.id) ^ (std::hash<std::string>()(key.name) << 1);
       }
   };
   
   int main() {
       // MyKeyHashni shablon parametr sifatida o'tkazamiz
       std::unordered_map<MyKey, int, MyKeyHash> myUnorderedMap;
       MyKey key1{1, "apple"};
       MyKey key2{2, "banana"};
       myUnorderedMap[key1] = 10;
       myUnorderedMap[key2] = 20;
       return 0;
   }
   

Har ikkala holatda ham, == tenglik operatori ham std::unordered_map uchun zarur.