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;
}