How do I find elements with custom comparators with std::unordered_map in performance-sensitive code?

In C++, when using std::unordered_map, the default hash function is based on the type of key and the default equality comparison. However, in performance-sensitive applications, you may need to find elements using custom comparators. This is essential for optimizing search times without resorting to the potential overhead of traditional data structures.

By defining custom hash and equality functions, you can improve the performance of your unordered map when dealing with complex types.

#include <iostream>
#include <unordered_map>
#include <string>

struct CustomHash {
    std::size_t operator()(const std::string& s) const {
        return std::hash<:string>()(s);
    }
};

struct CustomEqual {
    bool operator()(const std::string& lhs, const std::string& rhs) const {
        return lhs == rhs;
    }
};

int main() {
    std::unordered_map<:string int customhash customequal> myMap;
    myMap["example"] = 1;

    std::cout << "Value: " << myMap["example"] << std::endl;
    return 0;
}