【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", 1},
                             {"c", 3},
                             {"b", 2},
                             {"d", 4},
                             {"a", 6},
                             {"a", 9} };
    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 0;
}

 输出结果：