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();

}