问题描述
我想保存图形的外部节点。为此，我有以下代码（我展示了我认为与问题相关的部分，我确实有所有 #include 标头等...）：
typedef adjacency_list <
setS,vecS,undirectedS,property<vertex_index_t,int>,property<edge_index_t,int>
> simplegraph;
struct output_visitor : public planar_face_traversal_visitor{
int c = 0;
vector<int> vertexOuter;
vector<int> save_vertexOuter;
void begin_face(){cout << "New face: ";};
void end_face(){
if (c>3){
save_vertexOuter = vertexOuter;
}
cout << "End face "<< endl;
vertexOuter.clear();
c = 0;
};
};
struct vertex_output_visitor : public output_visitor
{
template <typename Vertex>
void next_vertex(Vertex v){
cout << v << " ";
vertexOuter.push_back(v);
c ++;
}
};
simplegraph BuildGraph(int i,vector<vector<int>> structureInfo){
// arguments of the function are not relevant here
// I am just passing graphs from a dataset
int j;
simplegraph g;
vector <int> adjList = structureInfo[i];
for(int j =0; j<adjList.size(); j++){
cout << adjList[j] << " ";
}
for (j = 0; j<adjList.size()-1; j+=2){
add_edge(adjList[j],adjList[j+1],g);
}
return g;
}
simplegraph tempGSN = BuildGraph(i,gs_N);
vector<vec_t> embedding(num_vertices(tempGSN));
bool is_planar = boost::boyer_myrvold_planarity_test(tempGSN,boost::boyer_myrvold_params::embedding = &embedding[0]);
if (is_planar){
vertex_output_visitor v_vis;
planar_face_traversal(tempGSN,&embedding[0],v_vis);
for (int j = 0; j < v_vis.save_vertexOuter.size()-1; j+=1 ){
Do something;}
}
到目前为止，代码在小图（num 节点
0 3 0 4 0 6 0 7 1 3 1 5 1 6 2 4 2 5 2 6 3 6 3 7 4 6 5 6
它回来了
New face: 0 3 1 5 2 4 End face
New face: 6 End face
New face: 7 End face
这没有意义。正确的外表面应该是 0 7 3 1 5 2 4。
如果您能帮助我发现问题，我将不胜感激。谢谢！
解决方法
将您的图形解释为边列表（不是邻接列表，因为这似乎没有意义）：
我发现你的 0 7 3 1 5 2 4 序列源于平面图表示：
所以我同意有什么地方不对劲。我清理/简化了您的代码，并将其扩展到潜在原因的偏移中，但没有任何偏移导致行为发生任何变化。
我获得的唯一见解 - 从上面的平面图和原始嵌入的输出中可以直观地看出，第 7 点正在产生问题。
v = 0: (0,3) (0,7) (0,6) (0,4)
v = 1: (1,5) (1,6) (3,1)
v = 2: (2,4) (2,6) (5,2)
v = 3: (3,1) (3,3)
v = 4: (0,4) (4,6) (2,4)
v = 5: (5,2) (5,6) (1,5)
v = 6: (0,6) (4,6)
v = 7: (0,7) (3,7)
如果您查看顶点 0 的边的顺序，您会注意到它们的顺时针顺序不一致（再次参考图像）。
这可能是一个错误，或者我误解了平面性测试算法的完整先决条件。我建议你向 Boost 开发者提出这个问题。
完整列表
这包括：
- various docs 中概述的可选 make_connected/make_biconnected_planar/make_maximum_planar 步骤
- 允许从输入中删除特定顶点的命令行选项
- 带有原始嵌入调试转储的原始代码
- 尝试规范排序和绘制代码（最终只是确认未正确生成嵌入）
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/planar_face_traversal.hpp>
#include <boost/graph/boyer_myrvold_planar_test.hpp>
#include <boost/graph/make_connected.hpp>
#include <boost/graph/make_biconnected_planar.hpp>
#include <boost/graph/make_maximal_planar.hpp>
#include <boost/graph/planar_canonical_ordering.hpp>
#include <boost/graph/chrobak_payne_drawing.hpp>
#include <boost/graph/graphviz.hpp>
#include <boost/fusion/adapted.hpp> // parsing
#include <boost/spirit/home/x3.hpp> // parsing
#include <iostream>
using SimpleGraph =
boost::adjacency_list<boost::setS,boost::vecS,boost::undirectedS,boost::property<boost::vertex_index_t,int>,boost::property<boost::edge_index_t,int>>;
using V = SimpleGraph::vertex_descriptor;
using E = SimpleGraph::edge_descriptor;
using Vs = std::vector<V>;
using Es = std::vector<E>;
using Structures = std::vector<Vs>;
using Embedding = std::vector<Es>;
struct Point { int x,y; };
using Drawing = std::vector<Point>;
struct output_visitor : public boost::planar_face_traversal_visitor {
void begin_traversal() const { std::cout << "Planar traversal:\n"; }
void begin_face() { std::cout << "Face:"; }
void end_face() const { std::cout << "\n"; }
void next_vertex(V v) { std::cout << " " << v; }
void next_edge(E e) const { std::cout << " " << e; }
void end_traversal() const { std::cout << "Done\n"; }
};
SimpleGraph BuildGraph(std::string_view input){
SimpleGraph g;
namespace x3 = boost::spirit::x3;
static const auto edge_
= x3::rule<E,std::pair<V,V> >{}
= x3::uint_ >> x3::uint_;
std::vector<std::pair<size_t,size_t> > edgeList;
if (not phrase_parse(input.begin(),input.end(),+edge_ >> x3::eoi,// grammar
x3::space,// skipper
edgeList))
throw std::runtime_error("BuildGraph");
for (auto [src,tgt] : edgeList)
if (not add_edge(src,tgt,g).second)
throw std::runtime_error("BuildGraph");
return g;
}
auto parse_cli(std::set<std::string_view> cli) {
auto extract = [&] (std::string_view name) {
bool yn = cli.count(name);
cli.erase(name);
return yn;
};
struct {
bool make_bi,make_max,traverse,dump,draw,dot;
std::set<V,std::greater<V> > to_remove; // descending!
} parsed{extract("--make_bi"),extract("--make_max"),extract("--traverse"),extract("--dump"),extract("--draw"),extract("--dot"),{}};
extract(""); // prevent zero-length options
for (auto opt : cli)
if (opt.front() != '-')
parsed.to_remove.insert(std::stoul(opt.data()));
return parsed;
}
int main(int argc,char** argv) {
auto const opts = parse_cli({ argv+1,argv+argc });
namespace P = boost::boyer_myrvold_params;
SimpleGraph g =
BuildGraph("0 3 0 4 0 6 0 7 1 3 1 5 1 6 2 4 2 5 2 6 3 6 3 7 4 6 5 6");
// remove some vertices?
for (auto removal : opts.to_remove) {
clear_vertex(removal,g);
}
for (auto removal: opts.to_remove) { // DESCENDING ORDER
remove_vertex(removal,g);
}
std::cout << "Input: ";
for (auto e : boost::make_iterator_range(edges(g))) {
std::cout << " " << e;
}
std::cout << "\n";
// some optional tests/preprocessing,didn't improve for given inputs
if (opts.make_bi || opts.make_bi) {
make_connected(g);
Embedding embedding(num_vertices(g));
boyer_myrvold_planarity_test(g,P::embedding = &embedding[0]);
make_biconnected_planar(g,embedding.data());
}
if (opts.make_max) {
Embedding embedding(num_vertices(g));
boyer_myrvold_planarity_test(g,P::embedding = &embedding[0]);
make_maximal_planar(g,embedding.data());
}
if (opts.dot) {
boost::write_graphviz(std::cout,g);
}
Embedding embedding(num_vertices(g));
auto emap = boost::make_iterator_property_map(
embedding.begin(),get(boost::vertex_index,g));
bool planar = boyer_myrvold_planarity_test(g,P::embedding = emap);
if (planar) {
if (opts.traverse) {
output_visitor v_vis;
planar_face_traversal(g,emap,v_vis);
}
if (opts.dump) {
std::cout << "Raw embedding:\n";
for (auto v : boost::make_iterator_range(vertices(g))) {
std::cout << "v = " << v << ":";
for (auto e : embedding.at(v)) {
std::cout << " " << e;
}
std::cout << "\n";
}
}
if (opts.draw) {
Vs ordering;
planar_canonical_ordering(g,std::back_inserter(ordering));
for (auto v : ordering) {
std::cout << " " << v;
}
std::cout << "\n";
Drawing drawing(num_vertices(g));
// Compute the straight line drawing
chrobak_payne_straight_line_drawing(g,ordering.begin(),ordering.end(),&drawing[0]);
std::cout << "The straight line drawing is: " << std::endl;
for (auto v : boost::make_iterator_range(vertices(g))) {
auto [x,y] = drawing.at(v);
std::cout << v << " -> (" << x << "," << y << ")\n";
}
}
} else {
std::cout << "Not planar\n";
}
return planar? 0 : 1;
}
原文：(--dump --traverse --make_bi)：
Input: (0,4) (0,7) (1,3) (1,5) (2,7) (4,6)
Planar traversal:
Face: 0 (0,3) 3 (3,1) 1 (1,5) 5 (5,2) 2 (2,4) 4 (0,4)
Face: 6 (0,6)
Face: 7 (0,7)
Done
Raw embedding:
v = 0: (0,7)
移除顶点 7：(--traverse 7) https://godbolt.org/z/7e3Mfx：
Input: (0,6)
Done
一些高级游览：--traverse --make_max 7 --draw https://godbolt.org/z/bbdba5：
Input: (0,3) 3 (0,3)
Face: 4 (0,6)
Face: 1 (1,3)
Face: 5 (1,5)
Face: 2 (2,4)
Done
0 1 5 2 4 6 3
The straight line drawing is:
0 -> (0,0)
1 -> (10,0)
2 -> (6,2)
3 -> (5,5)
4 -> (5,3)
5 -> (7,1)
6 -> (5,4)