[C++STL]map容器用法介绍

Posted 2021-06-27 Wecccccccc

代码如下:

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

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

void test01()
{
	map<int, int>m;
	m.insert(pair<int, int>(1, 10));
	m.insert(pair<int, int>(2, 20));
	m.insert(pair<int, int>(3, 30));
	m.insert(pair<int, int>(4, 40));
	printMap(m);

	map<int, int>m2(m);
	printMap(m2);

	map<int, int>m3;
	m3 = m2;
	printMap(m3);
}

int main()
{
	test01();
	return 0;
}

测试结果:

总结:
map中所有元素都是成对出现，插入数据时候要使用对组。

代码如下:

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

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

void test01()
{
	map<int, int>m;
	m.insert(pair<int, int>(1, 10));
	m.insert(pair<int, int>(2, 20));
	m.insert(pair<int, int>(3, 30));
	m.insert(pair<int, int>(4, 40));
	
	if (m.empty())
	{
		cout << "m empty" << endl;
	}
	else
	{
		cout << "m no empty" << endl;
		cout << "m size = " << m.size() << endl;
	}

	map<int, int>m2;
	m2.insert(pair<int, int>(4, 100));
	m2.insert(pair<int, int>(5, 200));
	m2.insert(pair<int, int>(6, 300));

	cout << "交换前" << endl;
	printMap(m);
	printMap(m2);

	cout << "交换后" << endl;
	printMap(m);
	printMap(m2);

}

int main()
{
	test01();
	return 0;
}

测试结果:

总结:

代码如下:

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

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

void test01()
{
	map<int, int>m;
	m.insert(pair<int, int>(1, 10));
	m.insert(make_pair(2, 20));
	m.insert(map<int, int>::value_type(3, 30));
	m[4] = 40;

	printMap(m);

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

	m.erase(3);
	printMap(m);

	m.erase(m.begin(), m.end());
	m.clear();
	printMap(m);

}

int main()
{
	test01();
	return 0;
}

测试结果:

总结:

代码如下:

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

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

void test01()
{
	map<int, int>m;
	m.insert(pair<int, int>(1, 10));
	m.insert(pair<int, int>(2, 20));
	m.insert(pair<int, int>(3, 30));
	m.insert(pair<int, int>(4, 40));

	map<int, int>::iterator pos = m.find(3);

	if (pos != m.end())
	{
		cout << "find key = " << (*pos).first << "value = " << (*pos).second << endl;
	}
	else
	{
		cout << "no find" << endl;
	}

	int num = m.count(3);
	cout << "num = " << num << endl;

}


int main()
{
	test01();
	return 0;
}

测试结果:

总结:

代码如下:

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

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

class cmp
{
public:
	bool operator()(int a, int b)
	{
		return a > b;
	}
};

void test01()
{
	map<int, int, cmp>m;
	m.insert(make_pair(1, 10));
	m.insert(make_pair(2, 20));
	m.insert(make_pair(3, 30));
	m.insert(make_pair(4, 40));
	m.insert(make_pair(5, 50));

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

}


int main()
{
	test01();
	return 0;
}

测试结果:

总结: