Using boost connected components with cartesian points - c++

Question

I found http://www.boost.org/doc/libs/1_49_0/libs/graph/example/incremental_components.cpp and want to check if it will work for me. How to convert this example to cope with cartesian points with (x,y) or (x,y,z). I can't find such example in documentation of boost.
I see that i must redefine vertice in some way, so change in adjacency_list is needed. Tried to change vecS with Point definifion, but i think also some changes in add_edge functions are needed.

Answer 1

I made a couple minor changes to the example you pointed too. Specifically setting the 4th & fifth template parameters on the adjacency_list to be the a type containing any additional vertex and edge properties. See docs here: http://www.boost.org/doc/libs/1_48_0/libs/graph/doc/adjacency_list.html
struct point
{
int x;
int y;
int z;
};
typedef adjacency_list <vecS, vecS, undirectedS, point > Graph;
After nodes & vertices the additional point data can be set like this:
graph[0].x = 42;
And retrieved at the end after the components have been computed:
std::cout << child_index << " " << "x=" << graph[current_index].x << " ";
Full code:
//=======================================================================
// Copyright 1997, 1998, 1999, 2000 University of Notre Dame.
// Copyright 2009 Trustees of Indiana University.
// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek, Michael Hansen
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//=======================================================================
#include <iostream>
#include <vector>
#include <boost/foreach.hpp>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graph_utility.hpp>
#include <boost/graph/incremental_components.hpp>
#include <boost/pending/disjoint_sets.hpp>
/*
This example shows how to use the disjoint set data structure
to compute the connected components of an undirected, changing
graph.
Sample output:
An undirected graph:
0 <--> 1 4
1 <--> 0 4
2 <--> 5
3 <-->
4 <--> 1 0
5 <--> 2
representative[0] = 1
representative[1] = 1
representative[2] = 5
representative[3] = 3
representative[4] = 1
representative[5] = 5
component 0 contains: 4 1 0
component 1 contains: 3
component 2 contains: 5 2
*/
using namespace boost;
struct point
{
point() : x(0), y(0), z(0) {}
int x;
int y;
int z;
};
int main(int argc, char* argv[])
{
typedef adjacency_list <vecS, vecS, undirectedS, point > Graph;
typedef graph_traits<Graph>::vertex_descriptor Vertex;
typedef graph_traits<Graph>::vertices_size_type VertexIndex;
const int VERTEX_COUNT = 6;
Graph graph(VERTEX_COUNT);
std::vector<VertexIndex> rank(num_vertices(graph));
std::vector<Vertex> parent(num_vertices(graph));
typedef VertexIndex* Rank;
typedef Vertex* Parent;
disjoint_sets<Rank, Parent> ds(&rank[0], &parent[0]);
initialize_incremental_components(graph, ds);
incremental_components(graph, ds);
graph_traits<Graph>::edge_descriptor edge;
bool flag;
boost::tie(edge, flag) = add_edge(0, 1, graph);
ds.union_set(0,1);
boost::tie(edge, flag) = add_edge(1, 4, graph);
ds.union_set(1,4);
boost::tie(edge, flag) = add_edge(4, 0, graph);
ds.union_set(4,0);
boost::tie(edge, flag) = add_edge(2, 5, graph);
ds.union_set(2,5);
graph[0].x = 42;
std::cout << "An undirected graph:" << std::endl;
print_graph(graph, get(boost::vertex_index, graph));
std::cout << std::endl;
BOOST_FOREACH(Vertex current_vertex, vertices(graph)) {
std::cout << "representative[" << current_vertex << "] = " <<
ds.find_set(current_vertex) << std::endl;
}
std::cout << std::endl;
typedef component_index<VertexIndex> Components;
// NOTE: Because we're using vecS for the graph type, we're
// effectively using identity_property_map for a vertex index map.
// If we were to use listS instead, the index map would need to be
// explicitly passed to the component_index constructor.
Components components(parent.begin(), parent.end());
// Iterate through the component indices
BOOST_FOREACH(VertexIndex current_index, components) {
std::cout << "component " << current_index << " contains: ";
// Iterate through the child vertex indices for [current_index]
BOOST_FOREACH(VertexIndex child_index,
components[current_index])
{
std::cout << child_index
<< " {" << graph[child_index].x
<< "," << graph[child_index].y
<< "," << graph[child_index].z << "} ";
}
std::cout << std::endl;
}
return (0);
}