STL map容器常用API

map容器：键值和实值是分开的，排序规则按照键值排序

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

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

//注意:map的排序规则，传入的参数不是pair类型，而是key类型
struct mycompare{
    bool operator()(int key1, int key2){
        return key1 > key2;
    }
};

//1. map容器的使用
void test01(){
    //map是否支持随机访问？不支持随机访问，双向迭代器

    //创建map容器
    map<int, string, mycompare> mymap;

    //1. 第一种插入方式
    mymap.insert(pair<int,string>(3,"aaa"));
    //2. 第二种插入方式
    mymap.insert(make_pair(6, "bbb"));
    //3. 第三种插入方式
    mymap.insert(map<int,string>::value_type(2,"ccc"));
    //4. 第四种插入方式
    mymap[4] = "ddd";
    mymap[4] = "eee";

    mymap.erase(2);

    printMap(mymap);

    //cout << "size:" << mymap.size() << endl;
    //如果使用[]号这种方式输出一个不存在的key的值，那么编译器会以指定key增加新的数据
    //如果使用[]号方式插入一条key存在的数据，那么已有数据会被修改
    //cout << mymap[100] << endl;
    //cout << "size:" << mymap.size() << endl;
}

//3. map查找操作
/*
find(key);//查找键key是否存在,若存在，返回该键的元素的迭代器；/若不存在，返回map.end();
count(keyElem);//返回容器中key为keyElem的对组个数。对map来说，要么是0，要么是1。对multimap来说，值可能大于1。
lower_bound(keyElem);//返回第一个key>=keyElem元素的迭代器。
upper_bound(keyElem);//返回第一个key>keyElem元素的迭代器。
equal_range(keyElem);//返回容器中key与keyElem相等的上下限的两个迭代器。
*/

void test02(){

    map<int, string> mymap;
    mymap.insert(make_pair(1, "aaa"));
    mymap.insert(make_pair(2, "bbb"));
    mymap.insert(make_pair(3, "ccc"));
    mymap.insert(make_pair(4, "ddd"));
    mymap.insert(make_pair(5, "eee"));

    map<int, string>::iterator it = mymap.find(30);
    if (it == mymap.end()){
        cout << "查找失败!" << endl;
    }
    else{
        cout << "Key:" << it->first << " Value:" << it->second << endl;
    }


    it = mymap.lower_bound(3);
    if (it == mymap.end()){
        cout << "查找失败!" << endl;
    }
    else{
        cout << "Key:" << it->first << " Value:" << it->second << endl;
    }

    it = mymap.upper_bound(3);
    if (it == mymap.end()){
        cout << "查找失败!" << endl;
    }
    else{
        cout << "Key:" << it->first << " Value:" << it->second << endl;
    }

    pair<map<int, string>::iterator, map<int, string>::iterator> ret =  mymap.equal_range(3);
    if (ret.first != mymap.end()){
        cout << "Key:" << ret.first->first << " Value:" << ret.first->second << endl;
    }
    if (ret.second != mymap.end()){
        cout << "Key:" << ret.second->first << " Value:" << ret.second->second << endl;
    }



}

int main(){

    //test01();
    test02();

    system("pause");
    return EXIT_SUCCESS;
}

map容器案例：员工分组案例

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<vector>
#include<string>
#include<map>
#include<ctime>
using namespace std;

//公司今天招聘了5个员工，5名员工进入公司之后，需要指派员工在那个部门工作
//人员信息有: 姓名 年龄 电话 工资等组成
//通过Multimap进行信息的插入 保存 显示
//分部门显示员工信息 显示全部员工信息

#define SALE_DEPATMENT 1 //销售部门
#define DEVELOP_DEPATMENT 2 //研发部门
#define FINACIAL_DEPATMENT 3 //财务部门

class Woker{
public:
    string mName;
    int mAge;
    int mSalary;
};

//创建员工
void CreateWorkers(vector<Woker> &vWorkers){

    srand((unsigned int)time(NULL));

    string nameSeed = "ABCDE";
    for (int i = 0; i < 5;i ++){
        Woker worker;
        worker.mName = "员工";
        worker.mName += nameSeed[i];
        worker.mAge = rand() % 30 + 30;
        worker.mSalary = rand() % 10000 + 10000;
        vWorkers.push_back(worker);
    }

}
//员工分组
void WokerByGroup(vector<Woker> &vWorkers, multimap<int, Woker>  &mWokers){

    //遍历员工
    for (vector<Woker>::iterator it = vWorkers.begin(); it != vWorkers.end(); ++it){
        
        int departmentID = rand() % 3 + 1;
        //员工保存在分组之后容器中
        mWokers.insert(make_pair(departmentID,*it));
    }

}

void Group(multimap<int, Woker>  &mWokers, int depID){

    multimap<int, Woker>::iterator  it = mWokers.find(depID);
    int mcount = mWokers.count(depID);
    int index = 0;
    for (; it != mWokers.end() && index < mcount; ++it, ++index){
        cout << "Name:" << it->second.mName << " Age:" << it->second.mAge << " Salary:" << it->second.mSalary << "美刀!" << endl;
    }
}
//打印各组员工信息
void PrintWorkers(multimap<int, Woker>  &mWokers){

    cout << "财务部门员工信息如下:" << endl;
    Group(mWokers, FINACIAL_DEPATMENT);
    cout << "研发部门员工信息如下:" << endl;
    Group(mWokers, DEVELOP_DEPATMENT);
    cout << "销售部门员工信息如下:" << endl;
    Group(mWokers, SALE_DEPATMENT);
}




int main(){

    vector<Woker> vWorkers;// 保存未分组的员工信息
    multimap<int, Woker>  mWokers; //保存分组后的员工信息

    CreateWorkers(vWorkers);
    WokerByGroup(vWorkers, mWokers);
    PrintWorkers(mWokers);

    system("pause");
    return EXIT_SUCCESS;
}