STL - map与multimap

更多参考我的另一篇博客：

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

  1 #include<iostream>
  2 #include<map>
  3 
  4 using namespace std;
  5 
  6 void printf(map<int, int> map_)
  7 {
  8     for (map<int, int>::iterator itr = map_.begin(); itr != map_.end(); itr++)
  9     {
 10         cout << "key = " << itr->first << " value = " << itr->second << endl;
 11     }
 12 }
 13 
 14 class Student
 15 {
 16 public:
 17     Student(int age, int num) :age_(age), num_(num) {};
 18 
 19     int age_;
 20     int num_;
 21 };
 22 
 23 // 仿函数写法1
 24 //class MyCompare
 25 //{
 26 //public:
 27 //    bool operator()(Student stu1, Student stu2)
 28 //    {
 29 //        return stu1.num_ > stu2.num_;
 30 //    }
 31 //};
 32 // 仿函数写法2
 33 struct  MyCompare
 34 {
 35 
 36     bool operator()(Student stu1, Student stu2)
 37     {
 38         return stu1.num_ > stu2.num_;
 39     }
 40 };
 41 
 42 
 43 int main()
 44 {
 45     // <1>初始化
 46     map<int, int> map_;
 47     map_.insert(pair<int, int>(10, 20)); // 1
 48     map_.insert(make_pair<int, int>(20, 20)); // 2
 49     pair<map<int, int>::iterator, bool> ret =  map_.insert(map<int, int>::value_type(20, 20)); // 3,返回插入成功？
 50     cout << "插入是否成功？ 答案是：" << ret.second << endl;
 51 
 52     map_[30] = 30; // 4
 53     map_[30] = 999;//修改已有键的值
 54     map_[40]++;// key = 40 之前不存在，这里value首先默认为 0
 55     printf(map_);
 56     // <2>
 57     // 仿函数【自定义排序规则】 
 58     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
 59     map1.insert(make_pair(Student(10, 100), 1));
 60     map1.insert(make_pair(Student(10, 300), 1));
 61     map1.insert(make_pair(Student(10, 300), 1)); // 插入失败
 62     map1.insert(make_pair(Student(10, 600), 1));
 63 
 64     // <3>操作符[] 与 at
 65     std::map<std::string, int> mymap = 
 66     {
 67         { "alpha", 0 },
 68         { "beta", 0 },
 69         { "gamma", 0 } 
 70     };
 71     mymap.at("alpha") = 10;
 72     mymap.at("beta") = 20;
 73     mymap["gamma"] = 30;
 74 
 75     for (auto& x:mymap) 
 76     {
 77         std::cout  << x.first.c_str()  << ": " << x.second << '\n';
 78     }
 79 
 80     // <4>区间操作
 81     {
 82         // lower_bound  and  upper_bound
 83         map<char, int> mymap;
 84         map<char, int>::iterator itlow, itup;
 85 
 86         mymap['a'] = 20;
 87         mymap['b'] = 40;
 88         mymap['c'] = 60;
 89         mymap['d'] = 80;
 90         mymap['e'] = 100;
 91 
 92         itlow = mymap.lower_bound('b');  // itlow points to b 指向等于b
 93         itup = mymap.upper_bound('d');   // itup points to e (not d!) 指向大于d
 94 
 95         mymap.erase(itlow, itup);        // erases [itlow,itup)
 96 
 97                                          // print content:
 98         for (std::map<char, int>::iterator it = mymap.begin(); it != mymap.end(); ++it)
 99             std::cout << it->first << " => " << it->second << '\n';
100 
101         // equal_range
102         map<int, int> mymap_;
103         mymap_.insert(make_pair(10, 100));
104         mymap_.insert(make_pair(20, 300));
105         mymap_.insert(make_pair(30, 200));
106         mymap_.insert(make_pair(40, 200));
107         mymap_.insert(make_pair(50, 200));
108         pair<map<int, int>::iterator, map<int, int>::iterator> ret;
109         ret = mymap_.equal_range(40);
110         if (ret.first->second)
111         {
112             cout << "找到lower_bound" << "【" << ret.first->first <<","<< ret.first->second << "】" << endl;
113         }
114         if (ret.second->second)
115         {
116             cout << "找到upper_bound" << "【" << ret.second->first << "," << ret.second->second << "】" << endl;
117         }
118     }
119     return 1;
120 }