C++-STL(11)-map-结构体指针作为key

map中如果要存的是结构体指针怎么做？
创建时：要重载 <函数，你得告诉Map如何排序。
查找时：重载==，你得告诉MAP何时相等。
删除时：delete外还要置空，因为是new的。
上代码：
 

#include <map>
#include <iostream>

using namespace std;

struct Key
{
    int x, y;
    bool operator==( const Key& b) const //需要重载==才能find
    {
        return x == b.x && y == b.y;
    }
};

struct CompareKey
{
    bool operator()(Key* a, Key* b)const //作为key得告诉map如何比较
    {
        return a->x < b->x;
    }


};


void map_key()
{
    cout<<"mapkey*************"<<endl;
    cout << "新建*************" << endl;
    map<Key*, int, CompareKey> mp;
    Key* findkey = NULL;
    for (int i = 0; i < 5; i++)
    {
        Key* k = new Key;
        k->x = i;
        k->y = i;
        mp.insert(make_pair(k, i));
        if (i == 2) { findkey = k; }
    }
    map<Key*, int, CompareKey>::iterator it;
    for (it = mp.begin(); it != mp.end(); it++)
    {
        if (it->first != nullptr)
        {
            cout << it->first->x << it->first->y << it->second << endl;
        }
    }
    cout << "查找*************" << endl;

    auto findit = mp.find(findkey);
    cout << findit->first->x << findit->first->y << findit->second << endl;
    cout << "删除*************" << endl;


    for (auto iter = mp.begin(); iter != mp.end(); ++iter)
    {
        auto first = iter->first;
        if (first->x == 3)
        {
            delete first;                 // 释放指针
            first = NULL;
            mp.erase(iter++);
        }
    }
    for (it = mp.begin(); it != mp.end(); it++)
    {
        if (it->first != nullptr)
        {
            cout << it->first->x << it->first->y << it->second << endl;
        }
    }
    cout << "释放*************" << endl;
    for (auto iter = mp.begin(); iter != mp.end(); )
    {
        auto first = iter->first;
        if (first)
        {
            delete first;                 // 释放指针
            first = NULL;
            mp.erase(iter++);            // 从map中删除元素，注意iter++的写法
        }
    }
    mp.clear();

}