Using an unordered_set - C++ STL

C++ examples for STL:unordered_set

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Description

Using an unordered_set

Demo Code

#include <cinttypes>
#include <functional>
#include <iostream>
#include <string>
#include <unordered_set>

using namespace std;

class SetObject;/*w  w  w. j  a  v a 2  s .  co m*/

namespace std
{
    template <>
    class hash<SetObject>
    {
    public:
        template <typename... Args>
        size_t operator()(Args&&... setObject) const
        {
            return hash<string>()((forward<Args...>(setObject...)).GetName());
        }
    };
}

class SetObject
{
private:
    string m_Name;
    size_t m_Hash{};
public:
    SetObject(const string& name)
        : m_Name{ name }
        , m_Hash{ hash<SetObject>()(*this) }
    {

    }

    const string& GetName() const
    {
        return m_Name;
    }

    const size_t& GetHash() const
    {
        return m_Hash;
    }

    bool operator==(const SetObject& other) const
    {
        return m_Hash == other.m_Hash;
    }
};

int main(int argv, char* argc[])
{
    unordered_set<SetObject> mySet;
    mySet.emplace("Five");
    mySet.emplace("Three");
    mySet.emplace("Four");
    mySet.emplace("One");
    mySet.emplace("Two");

    cout << showbase << hex;

    for (auto&& number : mySet)
    {
        cout << number.GetName() << " - " << number.GetHash() << endl;
    }

    auto iter = mySet.find({ "Three" });
    if (iter != mySet.end())
    {
        cout << "Found: " << iter->GetName() << " with hash: " << iter->GetHash() << endl;
    }

    return 0;
}

Result


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