1.map基本概念
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2.map构造和赋值
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cpp
#include <iostream>
using namespace std;
//map容器 构造和赋值
#include<map>
//遍历输出map容器
void printMap(const map<int, int>& m)
{
for (map<int, int>::const_iterator it = m.begin(); it != m.end(); it++)
{
cout << "key = " << (*it).first << "value = " << it->second << endl;
}
cout << endl;
}
void test01()
{
//创建map容器
map<int, int>m;
//按照key值自动排序
m.insert(pair<int, int>(1, 10));
m.insert(pair<int, int>(3, 30));
m.insert(pair<int, int>(2, 20));
m.insert(pair<int, int>(4, 40));
printMap(m);
//拷贝构造
map<int, int>m2(m);
printMap(m2);
//赋值
map<int, int>m3;
m3 = m2;
printMap(m3);
}
int main()
{
test01();
//cout << "-------------" << endl << endl;
//test02();
//**************************************
system("pause");
return 0;
}
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3.map大小和交换
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cpp
#include <iostream>
using namespace std;
//map容器 大小和交换
#include<map>
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;
}
//大小
void test01()
{
map<int, int>m;
m.insert(pair<int, int>(1, 10));
m.insert(pair<int, int>(3, 30));
m.insert(pair<int, int>(2, 20));
if (m.empty())
{
cout << "m为空!" << endl;
}
else
{
cout << "size of m : " << m.size() << endl;
}
}
//交换
void test02()
{
map<int, int>m;
m.insert(pair<int, int>(1, 10));
m.insert(pair<int, int>(3, 30));
m.insert(pair<int, int>(2, 20));
map<int, int>m2;
m2.insert(pair<int, int>(4, 100));
m2.insert(pair<int, int>(6, 300));
m2.insert(pair<int, int>(5, 200));
cout << "交换前:" << endl;
printMap(m);
printMap(m2);
//m与m2交换
m.swap(m2);
cout << "交换后:" << endl;
printMap(m);
printMap(m2);
}
int main()
{
test01();
cout << "-------------" << endl << endl;
test02();
//**************************************
system("pause");
return 0;
}
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4.map插入和删除
cpp
#include <iostream>
using namespace std;
//map容器 插入和删除
#include<map>
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()
{
//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, 20));
//第三种
m.insert(map<int, int>::value_type(3, 30));
//第四种
m[4] = 40;
//[]不建议插入, []其用途 可以利用可以访问到value
//cout << m[5] <<endl; //输出了" key = 5 value = 0 "
printMap(m);
//删除
m.erase(m.begin());
printMap(m);
m.erase(3); //按照key删除
printMap(m);
//清空
m.erase(m.begin(), m.end());
m.clear();
printMap(m);
}
int main()
{
test01();
//cout << "-------------" << endl << endl;
//test02();
//**************************************
system("pause");
return 0;
}
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5.map查找和统计
cpp
#include <iostream>
using namespace std;
//map容器 查找和统计
#include<map>
void test01()
{
//查找
map<int, int>m;
m.insert(make_pair(1, 10));
m.insert(make_pair(3, 30));
m.insert(make_pair(2, 20));
m.insert(make_pair(2, 40)); // 不能插入重复元素(以key为标准)
map<int, int>::iterator pos = m.find(3);
if (pos != m.end())
{
cout << "找到了该元素 key = " << (*pos).first << " value = " << pos->second << endl;
}
else
{
cout << "no find this element" << endl;
}
//统计
//map不允许插入重复元素, count统计而言 结果只能是0或1
//multimap的count统计可能大于1
int num = m.count(2);
cout << "num = " << num << endl;
}
int main()
{
test01();
//cout << "-------------" << endl << endl;
//test02();
//**************************************
system("pause");
return 0;
}
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6.map容器排序
cpp
#include <iostream>
using namespace std;
//map容器 排序
#include<map>
class MyCompare
{
public:
bool operator()(int v1, int v2) const
{
return v1 > v2; // 降序
}
};
void test01()
{
//默认从小到大排序
//利用仿函数实现从小到大排序
map<int, int, MyCompare> m;
m.insert(make_pair(1, 10));
m.insert(make_pair(3, 30));
m.insert(make_pair(2, 20));
for (map<int, int, MyCompare>::iterator it = m.begin(); it != m.end(); it++)
{
cout << "key = " << it->first << " value = " << it->second << endl;
}
}
int main()
{
test01();
//cout << "-------------" << endl << endl;
//test02();
//**************************************
system("pause");
return 0;
}
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