multimap

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  1. #include <iostream>
  2. #include <map>
  3. using namespace std;
  5. void main() {
  6.      typedef nultimap<int, double, less<int> > mmid;
  7.     mmid pairs;
  8.     cout << pairs.count(15) << endl; // 没有输出
  9.     pairs.insert(mmid::value_type(15, 2.7));
  10.     pairs.insert(mmid::value_type(15, 99.3));
  11.     // 输出 2
  12.     cout << pairs.count(15) << endl; // 求关键字等于某值的元素个数
  13.     pairs.insert(mmid::value_type(30, 111.11));
  14.     pairs.insert(mmid::value_type(10, 22.22));
  15.     pairs.insert(mmid::value_type(25, 22.22));
  16.     pairs.insert(mmid::value_type(20, 22.22));
  17.     for(mmid::const_iterator i = pairs.begin(); i != pairs.end(); ++i)
  18.         // (10, 22.22),(15,2.7),(15,99.3),(20,22.22),(25,22.22),(30,111.11)
  19.         cout << "(" << i->first << "," << i->second << ")" << ",";
  20. }

例题

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  1. #include <iostream>
  2. #include <cmap>
  3. #include <string>
  4. using namespace std;
  6. class Stu {
  7. public:
  8.     typedef struct { // 类的内部还可以定义类
  9.         int id;
  10.         string name;
  11.     }Info;
  12.     int score;
  13.     Info info;
  14. };
  15. typedef multimap<int, Stu::Info> MAP_STD;
  17. void main() {
  18.      MAP_STD mp;
  19.     Stu st;
  20.     string cmd;
  21.     while(cin >> cmd) {
  22.          if(cmd == "Add") {
  23.             cin >> st.info.name >> st.info.id >> st.score;
  24.             mp.insert(MAP_STD::value_type(st.score, st.info));
  25.         } else if (cmd == 'Query') {
  26.              int score;
  27.             cin >> score;
  28.             MAP_STD::iterator p = mp.lower_bound(score);
  29.             if(p != mp.begin()) {
  30.                  --p;
  31.                 score = p->first; // 比要查找的分数低的最高分
  32.                 MAP_STD::iterator maxp = p;
  33.                 int max_id = p->second->id;
  34.                 for(; p != mp.begin() && p->first == score; --p) {
  35.                      if(p->second.id > max_id) {
  36.                          maxp = p;
  37.                         max_id = p->second.id;
  38.                     }
  39.                 }
  40.                 if(p->first == score) { // 如果上面循环因为 p==mp.begin()而终止,还要再操作
  41.                     if(p->second.id > max_id) {
  42.                          maxp = p;
  43.                         max_id = p->second.id;
  44.                     }
  45.                 }
  46.                 cout << maxp->second.name << " " maxp->second.id << " " << maxp->first << endl;
  47.             } else { //lower_bound的结果就是 begin，说明没人分数比查询分数低
  48.                  cout << "Nobody" << endl;   
  49.             }
  50.         }
  51.     }
  52. }
  • 注意 lower_bound 的使用, p != mp.begin() 是关键
  • 插入还能这么写
    1. mp.insert(make_pair(st.score, st.info));

    map

    image.png

    map的[]成员函数

    image.png ```cpp

    include

    include

    using nanespace std;

void main() { typedef map > mmid; mmid pairs; cout << pairs.count(15) << endl; // 0 pairs.insert(mmid::value_type(15,2.7)); pairs.insert(make_pair(15, 2.7)); // 插入失败,如何判断见set cout << pairs.count(15) << endl; // 1 pairs.insert(mmid::value_type(20, 9.3)); mmid::iterator i ; for(i = pairs.begin(); i != pairs.end(); ++i) cout << *i << “ “; cout << endl; // (15,2.7) (20,9.3)

  1. int n = pairs[40]; // 如果没有关键字为40的元素,则插入一个
  2. for(i = pairs.begin(); i != pairs.end(); ++i)
  3.     cout << *i << ",";
  4. cout << endl; // (15,2.7),(20,9.3),(40,0),
  6. pairs[15] = 6.28;    // 把关键字为15的元素值改成6.28
  7. for(i = pairs.begin(); i != pairs.end(); ++i)
  8.     cout << *i << ",";
  9. cout << endl; // (15,6.28),(20,9.3),(40,0),

} ```