C++之map容器

map构造和赋值

#include<iostream>
#include<string>
using namespace std;
#include<map>

void printMap(map<int,int>&m)
{
	for (map<int,int>::iterator it = m.begin();it != m.end();it++)
	{
		//cout <<"key is: "<< (*it).first << " value is "<<(*it).second<<endl;
		cout << "key is: " << it->first << " value is " << it->second << endl;
	}
	cout << endl;
}

void test()
{
	//创建map容器
	map<int, int>m;

	m.insert(pair<int, int>(1, 10));
	m.insert(pair<int, int>(2, 50));
	m.insert(pair<int, int>(3, 30));
	m.insert(pair<int, int>(4, 20));
	m.insert(pair<int, int>(5, 40));

	printMap(m);

	//拷贝构造
	map<int, int>m2(m);
	printMap(m2);

	//赋值
	map<int, int>m3;
	m3 = m;
	printMap(m3);
}

int main()
{
	test();
	system("pause");
	return 0;
}

map大小和交换

#include<iostream>
#include<string>
using namespace std;
#include<map>

void printMap(map<int,int>&m)
{
	for (map<int,int>::iterator it = m.begin();it != m.end();it++)
	{
		//cout <<"key is: "<< (*it).first << " value is "<<(*it).second<<endl;
		cout << "key is: " << it->first << " value is " << it->second << endl;
	}
	cout << endl;
}

void test()
{
	//创建map容器
	map<int, int>m;

	m.insert(pair<int, int>(1, 10));
	m.insert(pair<int, int>(2, 50));
	m.insert(pair<int, int>(3, 30));
	m.insert(pair<int, int>(4, 20));
	m.insert(pair<int, int>(5, 40));

	printMap(m);

	if (m.empty())
	{
		cout << "m is empty" << endl;
	}
	else
	{
		cout << "m is not empty" << endl;
		cout << "m's size is" << m.size() << endl;
	}

	map<int, int>m2;

	m2.insert(pair<int, int>(1, 100));
	m2.insert(pair<int, int>(2, 500));
	m2.insert(pair<int, int>(3, 300));
	m2.insert(pair<int, int>(4, 200));
	m2.insert(pair<int, int>(5, 400));

	cout << "before swap" << endl;
	printMap(m);
	printMap(m2);

	m2.swap(m);
	cout << "after swap" << endl;
	printMap(m);
	printMap(m2);
}

int main()
{
	test();
	system("pause");
	return 0;
}

map插入和删除

#include<iostream>
#include<string>
using namespace std;
#include<map>

void printMap(map<int,int>&m)
{
	for (map<int,int>::iterator it = m.begin();it != m.end();it++)
	{
		//cout <<"key is: "<< (*it).first << " value is "<<(*it).second<<endl;
		cout << "key is: " << it->first << " value is " << it->second << endl;
	}
	cout << endl;
}

void test()
{
	//创建map容器
	map<int, int>m;

	//插入
	//第一种
	m.insert(pair<int, int>(1, 10));
	//第二种
	m.insert(make_pair(2, 50));
	//第三种
	m.insert(map<int, int>::value_type(3, 30));
	//第四种  不建议使用 用途：使用Key找到value
	m[4] = 20;

	printMap(m);

	//删除
	m.erase(m.begin());
	printMap(m);

	m.erase(2);//按照key值删除
	printMap(m);

	//清空
	//m.erase(m.begin(),m.end());
	m.clear();
	printMap(m);
}

int main()
{
	test();
	system("pause");
	return 0;
}

map查找和统计

#include<iostream>
#include<string>
using namespace std;
#include<map>

void printMap(map<int,int>&m)
{
	for (map<int,int>::iterator it = m.begin();it != m.end();it++)
	{
		//cout <<"key is: "<< (*it).first << " value is "<<(*it).second<<endl;
		cout << "key is: " << it->first << " value is " << it->second << endl;
	}
	cout << endl;
}

void test()
{
	//创建map容器
	map<int, int>m;

	//插入
	m.insert(pair<int, int>(1, 10));
	m.insert(pair<int, int>(2, 50));
	m.insert(pair<int, int>(3, 30));
	m.insert(pair<int, int>(4, 20));
	printMap(m);

	map<int,int>::iterator pos= m.find(2);
	if (pos != m.end())
	{
		cout << "找到了：key is " << pos->first << " value is " << (*pos).second << endl;
	}
	else
	{
		cout << "没有找到" << endl;
	}
//map不允许插入重复key 元素 ，count统计而言 结果要么是0 要么是1 
//multimap的count统计可能大于1
	//统计
	int num = m.count(3);//按照key查找
	cout << "num is " << num << endl;
}

int main()
{
	test();
	system("pause");
	return 0;
}

map容器排序

#include<iostream>
#include<string>
using namespace std;
#include<map>


class MyCompare
{
public:
	bool operator()(int v1, int v2)
	{
		return v1 > v2;
	}
};

void test()
{
	//创建map容器
	map<int, int, MyCompare>m;

	//插入
	m.insert(make_pair<int, int>(1, 10));
	m.insert(make_pair<int, int>(2, 50));
	m.insert(make_pair<int, int>(3, 30));
	m.insert(make_pair<int, int>(4, 20));

	for (map<int, int, MyCompare>::iterator it = m.begin();it != m.end();it++)
	{
		//cout <<"key is: "<< (*it).first << " value is "<<(*it).second<<endl;
		cout << "key is: " << it->first << " value is " << it->second << endl;
	}
	cout << endl;

}

int main()
{
	test();
	system("pause");
	return 0;
}