STL

更多参考我的另一篇博客：

https://www.cnblogs.com/winslam/articles/8975139.html

#include<iostream>
#include<map>

using namespace std;

void printf(map<int, int> map_)
{
    for (map<int, int>::iterator itr = map_.begin(); itr != map_.end(); itr++)
    {
        cout << "key = " << itr->first << " value = " << itr->second << endl;
    }
}

class Student
{
public:
    Student(int age, int num) :age_(age), num_(num) {};

    int age_;
    int num_;
};

// 仿函数写法1
//class MyCompare
//{
//public:
//    bool operator()(Student stu1, Student stu2)
//    {
//        return stu1.num_ > stu2.num_;
//    }
//};
// 仿函数写法2
struct  MyCompare
{

    bool operator()(Student stu1, Student stu2)
    {
        return stu1.num_ > stu2.num_;
    }
};


int main()
{
    // <1>初始化
    map<int, int> map_;
    map_.insert(pair<int, int>(10, 20)); // 1
    map_.insert(make_pair<int, int>(20, 20)); // 2
    pair<map<int, int>::iterator, bool> ret =  map_.insert(map<int, int>::value_type(20, 20)); // 3,返回插入成功？
    cout << "插入是否成功？ 答案是：" << ret.second << endl;

    map_[30] = 30; // 4
    map_[30] = 999;//修改已有键的值
    map_[40]++;// key = 40 之前不存在，这里value首先默认为 0
    printf(map_);
    // <2>
    // 仿函数【自定义排序规则】 
    map<Student, int, MyCompare> map1; //map/multimap本身会自动排序，所以这里无法对 class 进行排序，你必须自定义一个仿函数
    map1.insert(make_pair(Student(10, 100), 1));
    map1.insert(make_pair(Student(10, 300), 1));
    map1.insert(make_pair(Student(10, 300), 1)); // 插入失败
    map1.insert(make_pair(Student(10, 600), 1));

    // <3>操作符[] 与 at
    std::map<std::string, int> mymap = 
    {
        { "alpha", 0 },
        { "beta", 0 },
        { "gamma", 0 } 
    };
    mymap.at("alpha") = 10;
    mymap.at("beta") = 20;
    mymap["gamma"] = 30;

    for (auto& x:mymap) 
    {
        std::cout  << x.first.c_str()  << ": " << x.second << '
';
    }

    // <4>区间操作
    {
        // lower_bound  and  upper_bound
        map<char, int> mymap;
        map<char, int>::iterator itlow, itup;

        mymap['a'] = 20;
        mymap['b'] = 40;
        mymap['c'] = 60;
        mymap['d'] = 80;
        mymap['e'] = 100;

        itlow = mymap.lower_bound('b');  // itlow points to b 指向等于b
        itup = mymap.upper_bound('d');   // itup points to e (not d!) 指向大于d

        mymap.erase(itlow, itup);        // erases [itlow,itup)

                                         // print content:
        for (std::map<char, int>::iterator it = mymap.begin(); it != mymap.end(); ++it)
            std::cout << it->first << " => " << it->second << '
';

        // equal_range
        map<int, int> mymap_;
        mymap_.insert(make_pair(10, 100));
        mymap_.insert(make_pair(20, 300));
        mymap_.insert(make_pair(30, 200));
        mymap_.insert(make_pair(40, 200));
        mymap_.insert(make_pair(50, 200));
        pair<map<int, int>::iterator, map<int, int>::iterator> ret;
        ret = mymap_.equal_range(40);
        if (ret.first->second)
        {
            cout << "找到lower_bound" << "【" << ret.first->first <<","<< ret.first->second << "】" << endl;
        }
        if (ret.second->second)
        {
            cout << "找到upper_bound" << "【" << ret.second->first << "," << ret.second->second << "】" << endl;
        }
    }
    return 1;
}