问题描述
我已经在这里阅读了文档 (https://www.boost.org/doc/libs/1_75_0/libs/graph/doc/using_adjacency_list.html) 和几个堆栈溢出页面两个小时,但在这里根本没有取得任何进展。我有一个图表,其中边有距离和坑洞数量(撞到 3 个坑洞后车辆中断),所以我想我会使用自定义结构并设置边缘属性。
将其放在类声明之上:
struct road_details_t {
typedef boost::edge_property_tag kind;
};
struct road_info {
unsigned miles;
bool pothole;
};
typedef boost::property<road_details_t,struct road_info> RoadDetailsProperty;
编辑:我相信这是上述的替代方案,并且也没有运气:
namespace boost {
enum road_details_t { road_details };
BOOST_INSTALL_PROPERTY(edge,road_details);
}
类声明中的邻接图:
typedef boost::adjacency_list<boost::listS,// store edges in lists
boost::vecS,// store vertices in a vector
boost::undirectedS
RoadDetailsProperty
>
Graph;
typedef boost::graph_traits<Graph> GraphTraits;
typedef GraphTraits::vertex_descriptor Vertex;
typedef GraphTraits::edge_descriptor Edge;
Graph roadMap;
void City::addRoad(Intersection intersection1,Intersection intersection2,unsigned time,bool pothole)
{
unsigned nV = num_vertices(roadMap);
while (intersection1 >= nV)
nV = add_vertex(roadMap)+1;
while (intersection2 >= nV)
nV = add_vertex(roadMap)+1;
add_edge(intersection1,intersection2,roadMap);
所以现在我正在尝试输入/获取道路信息,该信息有多个错误并且我尝试了很多变体:
// get the edge
std::pair<Edge,bool> edg = edge(intersection1,roadMap);
// get the property map for road details. ERROR: no matching function call to get()
typename property_map<Graph,road_details_t>::type
roadDetailMap = get(road_details_t(),roadMap);
// create struct from arguments passed in
struct road_info info = {time,pothole};
// attempt to add to roadDetailMap
put(roadDetailMap,edg,info);
// roadDetailMap[edg] = info; // also not working
// attempt to fetch information
cout << get(roadDetailMap,edg).miles << endl;
// cout << roadDetailMap[edg].miles << endl; // also not working
通过注释掉各种行,我发现问题似乎出在我如何获取属性图上,但查看在线示例时,我觉得我正在做与它们完全相同的事情。
目标最终只是弄清楚如何添加道路信息以及如何在以后获取它,因此可以接受完全不同的方法,我在这里所拥有的只是我尝试过的(未成功)但我觉得取得了最有希望的结果。
解决方法
您可以按照您的建议进行操作,这需要使用 BOOST_INSTALL_PROPERTY
注册属性标记(请参阅 example/examples/edge_property.cpp for an example)。相关片段:
namespace boost {
enum edge_flow_t { edge_flow };
enum edge_capacity_t { edge_capacity };
BOOST_INSTALL_PROPERTY(edge,flow);
BOOST_INSTALL_PROPERTY(edge,capacity);
}
现在您可以在属性定义中使用新的属性标签 就像您使用内置标签之一一样。
typedef property<capacity_t,int> Cap;
typedef property<flow_t,int,Cap> EdgeProperty;
typedef adjacency_list<vecS,vecS,no_property,EdgeProperty> Graph;
然而,由于您的用例如此频繁,任何用户定义的结构都已经有一个内置标签:vertex_bundle_t
和 edge_bundle_t
:
捆绑属性
这是一个使用它的示例。文档:https://www.boost.org/doc/libs/1_75_0/libs/graph/doc/bundles.html
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graph_utility.hpp>
struct road_info {
unsigned miles;
bool pothole;
};
using Graph = boost::adjacency_list<boost::listS,boost::vecS,boost::undirectedS,road_info>;
using Vertex = Graph::vertex_descriptor;
using Edge = Graph::edge_descriptor;
int main() {
Graph roadMap;
Vertex road1 = add_vertex(road_info{15,false},roadMap);
Vertex road2 = add_vertex(road_info{3,true},roadMap);
/*Vertex road3 =*/ add_vertex(road_info{27,roadMap);
add_edge(road1,road2,roadMap);
print_graph(roadMap);
auto bmap = get(boost::vertex_bundle,roadMap);
for (Vertex v : boost::make_iterator_range(vertices(roadMap))) {
road_info& bundle = bmap[v];
// or even easier
// road_info& info = roadMap[v];
auto& [miles,pothole] = roadMap[v]; // c++17
std::cout << "Vertex #" << v << " " << miles << " miles,"
<< "pothole:" << std::boolalpha << pothole << "\n";
}
// individual maps
auto miles_map = get(&road_info::miles,roadMap);
auto poth_map = get(&road_info::pothole,roadMap);
for (Vertex v : boost::make_iterator_range(vertices(roadMap))) {
std::cout << "Vertex #" << v << " " << miles_map[v] << " miles,"
<< "pothole:" << std::boolalpha << poth_map[v] << "\n";
put(poth_map,v,false); // reset pothole
}
}
印刷品
0 <--> 1
1 <--> 0
2 <-->
Vertex #0 15 miles,pothole:false
Vertex #1 3 miles,pothole:true
Vertex #2 27 miles,pothole:false
Vertex #0 15 miles,pothole:false
更新:边缘包
对于评论,将其设为边包是肤浅的修改:
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graph_utility.hpp>
struct road_info {
unsigned miles;
bool pothole;
};
using Graph =
boost::adjacency_list<boost::listS,boost::no_property,road_info>;
using Vertex = Graph::vertex_descriptor;
using Edge = Graph::edge_descriptor;
int main() {
Graph roadMap(3);
add_edge(0,1,road_info{15,roadMap);
add_edge(1,2,road_info{3,roadMap);
print_graph(roadMap);
auto bmap = get(boost::edge_bundle,roadMap);
for (Edge e : boost::make_iterator_range(edges(roadMap))) {
road_info& bundle = bmap[e];
// or even easier
// road_info& info = roadMap[e];
auto& [miles,pothole] = roadMap[e]; // c++17
std::cout << "Edge " << e << " " << miles << " miles,roadMap);
for (Edge e : boost::make_iterator_range(edges(roadMap))) {
std::cout << "Edge " << e << " " << miles_map[e] << " miles,"
<< "pothole:" << std::boolalpha << poth_map[e] << "\n";
put(poth_map,e,false); // reset pothole
}
}
印刷:
0 <--> 1
1 <--> 0 2
2 <--> 1
Edge (0,1) 15 miles,pothole:false
Edge (1,2) 3 miles,pothole:true
Edge (0,pothole:true
对于受虐狂
如果你坚持,你当然可以安装一个属性标签。接触单个成员会让人不舒服(并且可能效率低下),但您做到了:
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graph_utility.hpp>
#include <boost/property_map/transform_value_property_map.hpp>
struct road_info {
unsigned miles;
bool pothole;
};
namespace boost {
struct edge_road_info_t {};
BOOST_INSTALL_PROPERTY(edge,road_info);
static inline constexpr edge_road_info_t road_info{};
}
using Graph =
boost::adjacency_list<boost::listS,boost::property<boost::edge_road_info_t,road_info> >;
using Vertex = Graph::vertex_descriptor;
using Edge = Graph::edge_descriptor;
int main() {
Graph roadMap(3);
add_edge(0,roadMap);
print_graph(roadMap);
auto info_map = get(boost::road_info,roadMap);
for (Edge e : boost::make_iterator_range(edges(roadMap))) {
road_info& info = info_map[e];
// or even easier
// road_info& info = roadMap[e];
auto& [miles,pothole] = info; // c++17
std::cout << "Edge " << e << " " << miles << " miles,"
<< "pothole:" << std::boolalpha << pothole << "\n";
}
// individual maps
auto miles_map = boost::make_transform_value_property_map(
std::mem_fn(&road_info::miles),info_map);
auto poth_map = boost::make_transform_value_property_map(
std::mem_fn(&road_info::pothole),info_map);
for (Edge e : boost::make_iterator_range(edges(roadMap))) {
std::cout << "Edge " << e << " " << miles_map[e] << " miles,false); // reset pothole
}
}
再次打印相同的输出。