map容器

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();
}