STL map用法总结(multimap)

2017-08-19 10:58:52 

writer;pprp

#include <map>
#include <string>
#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
typedef pair<int, string> PAIR;

ostream & operator<<(ostream & out, const PAIR& p)
{
    out << p.first << " " << p.second << endl;
    return out;
}

//函数对象，对（）进行了重载
struct CmpByValue
{
    bool operator()(const PAIR&l, const PAIR&r)
    {
        return l.second < r.second;
    }
};

int main()
{
    //数据插入
    map<int, string> mapStudent;

    mapStudent.insert(map<int, string>::value_type (1, "student_one"));
    mapStudent.insert(map<int, string>::value_type (2, "student_two"));
    mapStudent.insert(map<int, string>::value_type (3, "student_three"));
    mapStudent.insert(map<int, string>::value_type (4,"student_four"));
    mapStudent.insert(pair<int, string>(6, "student_six"));
    mapStudent.insert(make_pair(7, "student_seven"));
    mapStudent[5] = "student_five";

    //数据遍历
    //正向遍历
    map<int, string>::iterator  iter;
    for(iter = mapStudent.begin(); iter != mapStudent.end(); iter++)
    {
        cout<<iter->first<<" "<<iter->second<<endl;
    }
    //反向遍历
    map<int, string>::reverse_iterator it;
    for(it = mapStudent.rbegin(); it != mapStudent.rend() ; it++)
    {
        cout << it->first <<" " << it->second << endl;
    }
    //数组形式的遍历
    int nSize = mapStudent.size();
    for(int i = 0 ; i < nSize ; i++)
    {
        cout << mapStudent[i] << endl;
    }
    cout << endl;

    //数据的查找
    map<int, string>::iterator iter1;

    iter1 = mapStudent.find(1);

    if(iter1 != mapStudent.end())
    {
        cout << iter1->second << endl;
    }
    else
    {
        cout << "can't find it " << endl;
    }

    //判断是否存在这个key
    int judge = mapStudent.count(1);

    if(judge)
    {
        cout << "exist" << endl;
    }
    else
    {
        cout << "not exist"  << endl;
    }

    cout << endl;

    //用lower_bound进行查找
    map<int, string> :: iterator it2;
    it2 = mapStudent.lower_bound(2);
    cout << it2->second << endl;
    it2 = mapStudent.upper_bound(2);
    cout << it2->second << endl;

    pair<map<int, string>::iterator, map<int, string>::iterator> mapair;
    mapair = mapStudent.equal_range(1);
    //如果相等的话那就说明没有找到，如果不等就说明找到了
    if(mapair.first == mapair.second)
        cout << "can't find it" << endl;
    else
        cout << "the value of it is " << mapair.first->second << endl;

    //数据的清空与判空
//    mapStudent.clear();
    if(!mapStudent.empty())
        cout << "not empty" << endl;
    else
        cout << "empty" << endl;

    //数据的删除
    map<int, string> :: iterator it3;
    it3 = mapStudent.find(1);
    mapStudent.erase(it3);

    for(it3 = mapStudent.begin(); it3 != mapStudent.end(); it3++)
        cout << it3->second << endl;

    judge = mapStudent.erase(2);
    if(judge)
    {
        cout << "delete successfully" << endl;
        for(it3 = mapStudent.begin(); it3 != mapStudent.end(); it3++)
        {
            cout << it3->second << endl;
        }
    }

    //排序（按照key的大小排序）
    //map<int, string, less<int> >是默认的升序
    //map<int, string, greater<int> >是可以构造的降序

    //排序（按照value的大小排序）
    vector <PAIR> sortByValue(mapStudent.begin(), mapStudent.end());

    sort(sortByValue.begin(), sortByValue.end(),CmpByValue());

    for(int i = 0 ; i < mapStudent.size(); i++)
    {
        cout << sortByValue[i]<< endl;
    }
    return 0;
}

 另外multimap用法与map类似，函数什么的都一样，只是支持一个key对多个value

/*
name : usage of List
writer : pprp
declare : null
date ； 2017/8/20
*/
#include <bits/stdc++.h>

using namespace std;

void print(multimap<string,double>&k)
{
      multimap<string, double>::iterator it;
      for(it = k.begin(); it != k.end() ; it++)
      {
            cout << it->first << " " << it->second << endl;
      }
}

int main()
{
    multimap<string, double>mp;
    mp.insert(pair<string,double>("jack",300.23));
    mp.insert(make_pair("green",234.1));
    mp.insert(make_pair("red",234.132));
    mp.insert(make_pair("yellow",2342.1));
    mp.insert(make_pair("blue",234.11));
    mp.insert(make_pair("orange",2324.1));

    multimap<string, double>::iterator it;
    
    print(mp);
    
    mp.erase("jack");
    
    print(mp);
    
    it = mp.find("orange");
    if(it != mp.end())
    {
          cout << it->first << " " << it->second << endl;
    }

    return 0;
}