multimap的学习

小灰灰 2022-08-07 06:52 142阅读 0赞

#include <map>
    #include <iostream>
    using namespace std;
    
    
    
    void test_multimap()
    {
    //构造 multimap 的测试数据
      multimap<string, string> example;
      example.insert(make_pair(string("A"), string("11")));
      example.insert(make_pair(string("A"), string("22")));
      example.insert(make_pair(string("A"), string("33")));
    
      example.insert(make_pair(string("B"), string("44")));
      example.insert(make_pair(string("B"), string("55")));
      example.insert(make_pair(string("B"), string("66")));
    
      example.insert(make_pair(string("C"), string("77")));
      example.insert(make_pair(string("C"), string("88")));
      example.insert(make_pair(string("C"), string("99")));
    
      example.insert(make_pair(string("D"), string("000")));
      example.insert(make_pair(string("D"), string("111")));
      example.insert(make_pair(string("D"), string("222")));
    
      example.insert(make_pair(string("F"), string("0000")));
      example.insert(make_pair(string("F"), string("1111")));
      example.insert(make_pair(string("F"), string("2222")));
      example.insert(make_pair(string("F"), string("3333")));
    
      std::string del_item("A");
      multimap<string, string>::size_type count = example.erase(del_item);
    
      std::string search_item = "C";
      multimap<string, string>::iterator iter = example.find(search_item);
      multimap<string, string>::size_type all = example.count(search_item);
    //采用指定数量遍历
      for (multimap<string, string>::size_type cnt = 0; cnt < all; ++cnt, ++iter)
      {
        std::cout << iter->first << ":" << iter->second << endl;
      }
    
    //采用一个指定范围的迭代器遍历
      search_item = "B";
      for (iter = example.lower_bound(search_item); iter != example.upper_bound(search_item); ++iter)
      {
        std::cout << iter->first << ":" << iter->second << endl;
      }
    
    //使用成对迭代器来遍历元素
      search_item = "D";
      pair<multimap<string, string>::iterator, multimap<string, string>::iterator> pos;
      for (pos = example.equal_range(search_item); pos.first != pos.second; ++pos.first)
      {
        std::cout << pos.first->first << ":" << pos.first->second << endl;
      }
    
    //multimap 中删除元素
      search_item = "F";
      for (iter = example.begin(); iter != example.end();)
      {
        if (iter->second == "0000" || iter->second == "2222")
        {
          std::cout << "erase " << iter->first << ":" << iter->second << endl;
          example.erase(iter++);
        }
        else
        {
          iter++;
        }
      }
    
    //输出所有元素
      for (iter = example.begin(); iter != example.end(); ++iter)
      {
        std::cout << iter->first << ":" << iter->second << endl;
      }
    
    
    //查看multimap 的帮助文件,没有看到 multimap::operator[] 的定义,所以应该不支持
      //这个访问方式,就算支持,也不好定义其返回的值,比如 map 是这样定义的
      //Type& operator[](const Key& _Key);multimap 不好定义
    
    }
    
    int main(int argc, char *argv[])
    {
      test_multimap();
      return 0;
    }