multiset搬运

原作者：https://www.cnblogs.com/wenzhixin/p/8509909.html
额外：https://blog.csdn.net/sodacoco/article/details/84798621
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更新：有点点需要注意：https://blog.csdn.net/chenyijun/article/details/118892856

#include <set>
#include <string>
#include <iostream>
using namespace std;

struct myComp{
    bool operator () (const string &a,const string &b){
        if(a.compare(b) == 1)
            return 1;
        return 0;
    }
};

struct STUDENT{
    string name;
    double score;
    //重载"<"运算符，自定义排列规则
    bool operator < (const STUDENT &a) const{
        return a.score<score;//由大到小。如果由小到大，则符号为>
    }
};

void print(multiset<string> ms);
void rprint(multiset<string> ms);

int main()
{
    //多重集合的创建与插入
    multiset<string> ms;
    ms.insert("abc");
    ms.insert("123");
    ms.insert("111");
    ms.insert("aaa");
    ms.insert("123");
    cout<<"中序正向遍历：\n";
    print(ms);
    cout<<"中序逆向遍历：\n";
    rprint(ms);
    /*运行结果
    中序正向遍历：
    111
    123
    123
    aaa
    abc
    中序逆向遍历：
    abc
    aaa
    123
    123
    111
    */

    //元素的查找
    /*同set集合容器一样，使用find()查找元素，如果找到返回钙元素的迭代器位置（如果该元素存在重复，则返回第
    一个重复元素的迭代器位置），否则，返回end()迭代器*/
    multiset<string>:: iterator it;
    it=ms.find("123");
    if(it != ms.end()) cout<<"找到键值为123的元素\n";
    it=ms.find("456");
    if(it == ms.end()) cout<<"没有找到键值为456的元素\n";
    /*运行结果
    找到键值为123的元素
    没有找到键值为456的元素
    */

    //多重集合元素的删除
    cout<<"删除前:\n";
    print(ms);
    int n=ms.erase("123");//删除键值等于某个值得所有重复元素，并返回删除元素的个数
    cout<<"删除了"<<n<<"个元素\n";
    cout<<"删除后:\n";
    print(ms);
    /*运行结果
    删除前:
    111
    123
    123
    aaa
    abc
    删除了2个元素
    删除后:
    111
    aaa
    abc
    */

    ms.clear();
    if(ms.empty()) cout<<"清除后为：空\n";
    /*运行结果
    清除后为：空
    */

    /*同样在使用insert()可以采用自定义比较函数,默认从小到大*/
    //当元素类型是基本数据类型时，采用在主函数前重载"()"操作符
    multiset<string,myComp> mss;
    mss.insert("abc");
    mss.insert("123");
    mss.insert("111");
    mss.insert("aaa");
    mss.insert("123");

    multiset<string>::iterator it1;
    for(it1= mss.begin(); it1 != mss.end(); it1 ++){
        cout<<*it1<<endl;
    }
    /*运行结果
    abc
    aaa
    123
    123
    111
    */

    //如果元素是结构体，可以将比较函数写在结构体内，见main函数之前的定义方法
    multiset<STUDENT> students;
    STUDENT someone;
    someone.name="Jack";
    someone.score=80.5;
    students.insert(someone);

    someone.name="Tomi";
    someone.score=57.5;
    students.insert(someone);

    someone.name="Nacy";
    someone.score=60.5;
    students.insert(someone);

    someone.name="Nacy";
    someone.score=60.5;
    students.insert(someone);

    multiset<STUDENT>:: iterator it2;
    for(it2 = students.begin(); it2 != students.end(); it2 ++){
        cout<<(*it2).name<<":"<<(*it2).score<<endl;
    }
    /*运行结果
    Jack:80.5
    Nacy:60.5
    Nacy:60.5
    Tomi:57.5
    */
    return 0;
}

void print(multiset<string> ms)
{
    multiset<string>:: iterator it;
    for(it=ms.begin(); it != ms.end(); it ++){
        cout<<*it<<endl;
    }
}

void rprint(multiset<string> ms)
{
    multiset<string>::reverse_iterator rit;
    for(rit=ms.rbegin(); rit != ms.rend(); rit++){
        cout<<*rit<<endl;
    }
}