我有以下代码:
#include <iostream>
#include "boost/unordered_map.hpp"
using namespace std;
using namespace boost;
int main()
{
typedef unordered_map<int, int> Map;
typedef Map::const_iterator It;
Map m;
m[11] = 0;
m[0] = 1;
m[21] = 2;
for (It it (m.begin()); it!=m.end(); ++it)
cout << it->first << " " << it->second << endl;
return 0;
}
但是，我正在寻找保留顺序的东西，以便以后我可以按照插入元素的相同顺序遍历元素。在我的电脑上，上面的代码不保留顺序，并打印以下内容:
0 1
11 0
21 2
我想也许我可以使用 boost::multi_index_container
typedef multi_index_container<
int,
indexed_by<
hashed_unique<identity<int> >,
sequenced<>
>
> Map;
有人可以告诉我如何使用这个容器(或任何其他合适的容器)实现我的原始代码，以便迭代器遵循插入顺序吗？
#include <iostream>
#include "boost/unordered_map.hpp"
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/hashed_index.hpp>
#include <boost/multi_index/sequenced_index.hpp>
using namespace std;
using namespace boost;
using namespace boost::multi_index;
struct key_seq{};
struct key{};
struct Data_t
{
int key_;
int data_;
Data_t (int key_v, int data_v) : key_(key_v), data_(data_v) {}
};
int main()
{
typedef multi_index_container<
Data_t,
indexed_by<
hashed_unique<tag<key>, BOOST_MULTI_INDEX_MEMBER(Data_t,int,key_)>,
sequenced<tag<key_seq> >
>
> Map;
typedef Map::const_iterator It;
typedef index<Map,key>::type Map_hashed_by_key_index_t;
typedef index<Map,key>::type::const_iterator Map_hashed_by_key_iterator_t;
typedef index<Map,key_seq>::type Map_sequenced_by_key_index_t;
typedef index<Map,key_seq>::type::const_iterator Map_sequenced_by_key_iterator_t;
Map m;
m.insert(Data_t(11,0));
m.insert(Data_t(0,1));
m.insert(Data_t(21,1));
{
cout << "Hashed values\n";
Map_hashed_by_key_iterator_t i = get<key>(m).begin();
Map_hashed_by_key_iterator_t end = get<key>(m).end();
for (;i != end; ++i) {
cout << (*i).key_ << " " << (*i).data_ << endl;
}
}
{
cout << "Sequenced values\n";
Map_sequenced_by_key_iterator_t i = get<key_seq>(m).begin();
Map_sequenced_by_key_iterator_t end = get<key_seq>(m).end();
for (;i != end; ++i) {
cout << (*i).key_ << " " << (*i).data_ << endl;
}
}
return 0;
}