在stl中自定义map比较函数有两种方式，方式一在类中重载<操作符，方式二仿比较函数

1、方式一：重载<操作符

#include "stdafx.h"
#include <map>
#include <string>
#include <iostream>
using namespace std;

class Key
{
public:
	Key(string name, int age)
	{
		this->name=name;
		this->age=age;
	}
	~Key(){}
	string getName()
	{
		return name;
	}
	int getAge()
	{
		return age;
	}
	bool operator<(const Key& key) const
	{
		if(age!=key.age)
		{
			return age<key.age; 
		}
		else
		{
			return false;
		}
	}
private:
	string name;
	int age;
};

int main(void)
{
	Key key1("cjc",25);
	Key key2("ldb",26);
	Key key3("jzm",27);

	map<Key,string> s;
	s[key1]="He is a boy.";
	s[key2]="He is a student.";
	s[key3]="He is a old man.";

	map<Key,string>::iterator it=s.begin();
	while(it!=s.end())
	{
		cout<<"Name : "<<((Key)it->first).getName()<<endl;
		cout<<"Age : "<<((Key)it->first).getAge()<<endl;
		cout<<"Desc : "<<it->second<<endl;
		cout<<"--------------------------------------"<<endl;
		it++;
	}

	system("pause");
	return 0;
}

2、方式二：仿比较函数

#include "stdafx.h"
#include <map>
#include <string>
#include <iostream>
using namespace std;

typedef struct key
{
	string name;
	int age;
}Key;

struct cmpKey
{
	bool operator()(const Key& key1, const Key& key2)
	{
		if(key1.age!=key2.age)
		{
			return key1.age<key2.age;
		}
		else
		{
			return false;
		}
	}
};

int _tmain(int argc, _TCHAR* argv[])
{
	map<Key,string,cmpKey> s;

	Key key1,key2,key3;
	
	key1.age=24;
	key1.name="cjc";
	s[key1]="He is a boy!";

	key2.age=24;
	key2.name="ldb";
	s[key2]="He is a student!";

	key3.age=26;
	key3.name="jzm";
	s[key3]="He is an old man!";

	map<Key,string,cmpKey>::iterator it=s.begin();
	while(it!=s.end())
	{
		cout<<"Age : "<<it->first.age<<endl;
		cout<<"Name : "<<it->first.name<<endl;
		cout<<"Desc : "<<it->second<<endl;
		cout<<"---------------------------------"<<endl;
		it++;
	}

	system("pause");
	return 0;
}

stl中map自定义比较函数