Standard Template Library Basis [5] Map

说明：代码均省略其输出验证步骤

[1] map的插入元素

#include<iostream>
#include<functional>
#include<vector>
#include<algorithm>
#include<iterator>
#include<set>
#include<map>//map 和 multimap
#include<string>
#include<utility>
using namespace std;
int main()
{
    //m按照键值从小到大排序，键不能重复，值可以重复
    map<int,string> m;
    m[10]="alice";
    m[15]="lisan";

    
    //插入方法一：输出时会偷偷在m里面插入键值对
    cout<<m[10]<<endl;
    cout<<m[-200]<<endl;//此时插入键为-200，值为空字符
    
    //插入方式二
    m.insert(make_pair(-100,"zhaosi"));
    
    //插入方法三
    m.insert(pair<int,string>(-300,"wangwu"));
    
    //插入方法四
    m.insert(map<int,string>::value_type(-400,"wangwu"));
    
    //插入方法五 C++11标准
    m.insert({-500,"lisan"});
    m.insert({{-700,"lisan"},{-600,"lisan"}});
    
    //输出
    for(map<int,string>::iterator p=m.begin();p!=m.end();p++)
    {
        printf("key:%5d value:%10s\n",p->first,p->second.c_str());
    }
    return 0;
}

[2]在定义的初步就给出map中的键值对

#include<iostream>
#include<functional>
#include<vector>
#include<algorithm>
#include<iterator>
#include<set>
#include<map>//map 和 multimap
#include<string>
#include<utility>
using namespace std;
int main()
{
    //定义的时候给出map里面的键值对
    pair<int, string> a(30,"lisan");
    pair<int, string> b(40,"wangwu");
    pair<int, string> c(50,"zhaosi");
    vector<pair<int,string>> a1;
    a1.push_back(a);
    a1.push_back(b);
    a1.push_back(c);
    map<int, string> m(a1.begin(),a1.end());
    
    //C++11
    map<int,string> m1={{1,"a"},{2,"b"},{3,"c"}};
    
    //拷贝构造函数也可以用
    //【注意】map里插入已有键的键值对的时候，新插入失败，保留原有键值对。multimap则不会失败
    
    return 0;
}

[3].empty(), .size(), .count(), .find(), upper_bound()和lower_bound

#include<iostream>
#include<functional>
#include<vector>
#include<algorithm>
#include<iterator>
#include<set>
#include<map>//map 和 multimap
#include<string>
#include<utility>
using namespace std;
int main()
{
    //m.empty()
    map<int,string> m;
    m[1]="lisan";
    m[2]="zhaosi";
    cout<<m.empty()<<endl;
    
    //m.size()
    cout<<m.empty()<<endl;
    
    //m.count()查找某个键的个数
    cout<<m.count(1)<<endl;
    
    //迭代子find()
    map<int,string>::iterator p1=m.find(1);
    cout<<p1->first<<" "<<p1->second.c_str()<<endl;
    
    //p可以用于键值对的删除
    m.erase(p1);
   
    //multiset中间删除同一个键的多个元素：lower_bound 和 upper_bound
    multimap<int,string> mm;
    mm.insert(make_pair(1,"Der Tod"));
    mm.insert(make_pair(1,"Elisabeth"));
    mm.insert(make_pair(1,"Rudolf"));
    mm.insert(make_pair(2,"Elisabeth"));
    
    //某一个键全部去掉 lower_bound和upper_bound
    multimap<int,string>::iterator p2=mm.lower_bound(1);
    multimap<int,string>::iterator p3=mm.upper_bound(1);
    //mm.erase(p2,p3);
    
    //以上操作也可以用equal_range替代
    pair<multimap<int,string>::iterator,multimap<int,string>::iterator> pp;
    pp=mm.equal_range(1);
    mm.erase(pp.first, pp.second);
    
    //将所有的键值都输出(p1和p2做循环)
    
    return 0;
}

[5]应用：删除某特定值的所有键值对

#include<iostream>
#include<functional>
#include<vector>
#include<algorithm>
#include<iterator>
#include<set>
#include<map>//map 和 multimap
#include<string>
#include<utility>
using namespace std;
int main()
{
    //删除某特定值的所有键值对
    multimap<int,string> mm;
    mm.insert(make_pair(1,"Der Tod"));
    mm.insert(make_pair(1,"Elisabeth"));
    mm.insert(make_pair(1,"Rudolf"));
    mm.insert(make_pair(2,"Elisabeth"));
    
    for(multimap<int,string>::iterator p=mm.begin();p!=mm.end();)
    {
        if(p->second=="Elisabeth")
        {
            mm.erase(p++);
            continue;
        }
        else
        {
            p++;
        }
    }
    return 0;
}

[6]例子：三维的点对应按原点对称的点

#include<iostream> 
#include<map> 
#include<string> 
#include<utility> 
#include<vector>
using namespace std; //map
class Point
{
public:
    Point(int _x, int _y, int _z)
    {
        x = _x;
        y = _y;
        z = _z;
    }
    Point()
    {
    }
    bool operator< (const Point &p) const
    {
        return this->x < p.x;
    }
    void ShowPoint() const
    {
        printf("x=%4d y=%04d z=%04d", x, y, z);
    }
    int x;
    int y;
    int z;
};
int main()
{
    Point a(10, 30, 50);
    Point b(-5, 50, 70);
    Point c(0, 0, 0);
    map<Point,Point> m;
    m[a] = Point(-a.x, -a.y, -a.z);
    m[b] = Point(-b.x, -b.y, -b.z);
    m[c] = Point(-c.x, -c.y, -c.z);
    for (map<Point, Point>::iterator p = m.begin();p != m.end();p++)
    {
        (p->first).ShowPoint();
        cout << " ";
        (p->second).ShowPoint();
        cout << endl;
    }
    return 0;
}