【C++ Primer | 11】关联容器（一）

在multimap或multiset中查找元素

第二种方法解释：

 #include <iostream>
 #include <utility>
 #include <iterator>
 #include <functional>
 #include <algorithm>
 #include <map>
 #include <set>
 #include <string>
 using namespace std;
 
 int main()
 {
     pair<string, int> p[] = { {"a", },
                              {"c", },
                              {"b", },
                              {"d", },
                              {"a", },
                              {"a", } };
     multimap<string, int> mm(begin(p), end(p));
     for (auto q : mm)
     {
         cout << q.first << " " << q.second << endl;
     }
     //第一种方法 find+count
     string search_item("a");
     auto entries = mm.count(search_item);
     auto iter = mm.find(search_item);
     while (entries)
     {
         cout << iter->second << endl;
         ++iter;
         --entries;
     }
     //第二种方法：面向迭代器的解决方法
     for (auto beg = mm.lower_bound(search_item), end = mm.upper_bound(search_item); beg != end; ++beg)
     {
         cout << beg->second << " ";
     }
     //第二种方法：利用equal_range函数
     for (auto pos = mm.equal_range(search_item); pos.first != pos.second; ++pos.first)
     {
         cout << pos.first->second << " ";
     }
     system("pause");
     return ;
 }

输出结果：