目录
map构造和赋值
map大小和交换
map插入和删除
map查找和统计
map排序
map构造和赋值
map中所有元素都是pair(即一对)
pair中第一个元素为key(键值),起到索引作用,第二个元素为value(实值)
所有元素根据元素键值自动排序
//author:至尊宝
//time:2024.5.9
#include<iostream>
#include<cstring>
#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);
//拷贝构造
map<int, int>m2(m);
printMap(m2);
//赋值
map<int, int>m3;
m3 = m2;
printMap(m3);
}
int main()
{
test01();
}
map大小和交换
size()返回容器中元素的数目
empty()判断容器是否为空
swap()交换两个集合容器
//author:至尊宝
//time:2024.5.9
#include<iostream>
#include<cstring>
#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));
if (m.empty())
{
cout << "m为空" << endl;
}
else
{
cout << "m不为空" << endl;
cout << "m的大小为:" << m.size() << endl;
}
}
//交换
void test02()
{
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));
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;
m.swap(m2);
printMap(m); printMap(m2);
}
int main()
{
test02();
}
map插入和删除
insert()在容器中插入元素
clear()清除所有元素
erase(pos)删除pos迭代器所指的元素,返回下一个元素的迭代器
erase(beg,end)删除区间beg,end的所有元素,返回下一个元素的迭代器
erase(key)删除容器中值为key的元素
//author:至尊宝
//time:2024.5.9
#include<iostream>
#include<cstring>
#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;
//插入
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;
//删除
m.erase(m.begin());
printMap(m);
m.erase(3);//按照key来删
printMap(m);
m.erase(m.begin(), m.end());//==m.clear()
printMap(m);
}
//交换
void test02()
{
}
int main()
{
test01();
}
map查找和统计
find(key)查找key是否存在,返回该键的元素的迭代器,若不存在,返回set.end()
count(key)统计key元素个数
//author:至尊宝
//time:2024.5.9
#include<iostream>
#include<cstring>
#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));
map<int, int>::iterator pos = m.find(3);
if (pos != m.end())
{
cout << "找到了元素:key = " << (*pos).first << " value = " << (*pos).second << endl;
}
else
{
cout << "no" << endl;
}
//统计
//map不允许插入重复的key元素
int num = m.count(3);
cout << num;
}
void test02()
{
}
int main()
{
test01();
}
map排序
//author:至尊宝
//time:2024.5.9
#include<iostream>
#include<cstring>
#include<map>
using namespace std;
class MyCompare
{
public:
bool operator()(int v1,int v2)const
{
//降序
return v1 > v2;
}
};
void test01()
{
map<int, int, MyCompare>m;
m.insert(pair<int, int>(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));
m.insert(make_pair(6, 60));
for (map<int, int, MyCompare>::iterator it = m.begin(); it != m.end(); it++)
{
cout << "key = " << it->first << " value = " << it->second << endl;
}
}
int main()
{
test01();
}