Re: [Boost-users] Newbie: BGL & planar graphs

The graph is planar. Hint: it does not contain neither a K5 complete graph nor a K3,3 bipartite graph (see Kuratowski's theorem) lc On Sun, Dec 3, 2017 at 2:29 AM, ano kato via Boost-users wrote:

Hello everyone!

I am using BGL to test for the planarity of drawings of graphs. The coordinates are hardcoded into the source code. Here's what the graph should look like: https://i.imgur.com/UGA0mRB.png. This definitely isn't planar and yet is_straight_line_drawing() returns 1! I'm quite confused. Am I doing something wrong? Thank you to anyone who replies.

#include <iostream> #include <vector> #include #include #include

using namespace boost;

typedef struct { size_t x,y; } coord_t;

int main(void) {

typedef adjacency_list > graph;

graph Moser(7); add_edge(0,1,Moser); add_edge(0,6,Moser); add_edge(0,4,Moser); add_edge(1,6,Moser); add_edge(1,2,Moser); add_edge(2,6,Moser); add_edge(2,5,Moser); add_edge(2,3,Moser); add_edge(3,4,Moser); add_edge(4,5,Moser);

graph G(Moser); int k = num_vertices(G);

typedef std::vector cvec; typedef boost::iterator_property_map ::type // ? > foo_t;

cvec v(num_vertices(G)); foo_t drawing(v.begin(), get(vertex_index, G));

coord_t x[k]; x[0].x = 20; x[0].y = 10; x[1].x = 50; x[1].y = 10; x[2].x = 58; x[2].y = 52; x[3].x = 00; x[3].y = 30; x[4].x = 35; x[4].y = 50; x[5].x = 12; x[5].y = 51; x[6].x = 70; x[6].y = 30;

graph_traits<graph>::vertex_iterator vi, vi_end; for(boost::tie(vi, vi_end) = vertices(G); vi != vi_end; ++vi) put(drawing, *vi, x[*vi]); if(is_straight_line_drawing(G,drawing)) std::cout << "This is a straight line planar drawing!" << std::endl; return 0; }

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