C++ 之 unordered_map——哈希表

#include 
#include 
#include 

using namespace std;

class Myclass
{
public:
    int first;
    vector<int> second;

    // 重载等号，判断两个Myclass类型的变量是否相等
    bool operator== (const Myclass &other) const
    {
        return first == other.first && second == other.second;
    }
};

// 实现Myclass类的hash函数
namespace std
{
    template <>
    struct hash
    {
        size_t operator()(const Myclass &k) const
        {
            int h = k.first;
            for (auto x : k.second)
            {
                h ^= x;
            }
            return h;
        }
    };
}

int main()
{
    unordered_mapdouble> S;
    Myclass a = { 2, {3, 4} };
    Myclass b = { 3, {1, 2, 3, 4} };
    S[a] = 2.5;
    S[b] = 3.123;
    cout << S[a] << ' ' << S[b] << endl;
    return 0;
}