如何在提振给出vertex_descriptor的:: grid_graph

Question

我试图改变边缘的重量在我grid_graph但未能与访问edge_descriptor的访问edge_descriptor的：

std::pair<bEdgeDescriptor, bool> ed_right = boost::edge(bVertexDescriptor {{i - 1, j, k}}, bVertexDescriptor {{i, j, k}}, grid); 

其中grid是boost::grid_graph<3>

然后我发现grid_graph不支持这个。为了使用astar_search，是否有任何方便的方式访问edge_descriptor与给定vertex_descriptor在boost::grid_graph但不是adjacency_list？

Answer 1

你可以得到内/外边缘对于任何特定的节点：

http://www.boost.org/doc/libs/1_63_0/libs/graph/doc/grid_graph.html#indexing

// Get the out-edge associated with vertex and out_edge_index 
Traits::edge_descriptor 
out_edge_at(Traits::vertex_descriptor vertex, 
      Traits::degree_size_type out_edge_index, 
      const Graph& graph); 

// Get the out-edge associated with vertex and in_edge_index 
Traits::edge_descriptor 
in_edge_at(Traits::vertex_descriptor vertex, 
      Traits::degree_size_type in_edge_index, 
      const Graph& graph); 

使用3D型4x4x4格非包装尺寸（演示这个节目，案件边缘上的节点程度较低）：

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#include <boost/graph/grid_graph.hpp> 
#include <boost/graph/adjacency_list.hpp> 
#include <iostream> 

using Grid = boost::grid_graph<3>; 
using Traits = boost::graph_traits<Grid>; 
using vertex_descriptor = Grid::vertex_descriptor; 
using edge_descriptor = Grid::edge_descriptor; 

static inline std::ostream& operator<<(std::ostream& os, vertex_descriptor const& vd) { 
    return os << "(" << vd[0] << ", " << vd[1] << ", " << vd[2] << ")"; 
} 

void print_in_edges(vertex_descriptor vd, Grid const& grid) { 
    for (Traits::degree_size_type ei = 0; ei < in_degree(vd, grid); ++ei) { 
     auto ed_left = in_edge_at(vd, ei, grid); 
     std::cout << "Detected in edge: " << ed_left.first << " -> " << ed_left.second << "\n"; 
    } 
} 

void print_out_edges(vertex_descriptor vd, Grid const& grid) { 
    for (Traits::degree_size_type ei = 0; ei < out_degree(vd, grid); ++ei) { 
     auto ed_left = out_edge_at(vd, ei, grid); 
     std::cout << "Detected out edge: " << ed_left.first << " -> " << ed_left.second << "\n"; 
    } 
} 

int main() { 
    Grid grid({ { 4, 4, 4 } }, false); 

    print_in_edges({{ 2, 2, 2 } }, grid); 
    print_out_edges({{ 2, 2, 2 } }, grid); 
    std::cout << "----\n"; 
    print_in_edges({{ 0, 0, 0 } }, grid); 
    print_out_edges({{ 0, 0, 0 } }, grid); 
} 

打印：

Detected in edge: (1, 2, 2) -> (2, 2, 2) 
Detected in edge: (3, 2, 2) -> (2, 2, 2) 
Detected in edge: (2, 1, 2) -> (2, 2, 2) 
Detected in edge: (2, 3, 2) -> (2, 2, 2) 
Detected in edge: (2, 2, 1) -> (2, 2, 2) 
Detected in edge: (2, 2, 3) -> (2, 2, 2) 
Detected out edge: (2, 2, 2) -> (1, 2, 2) 
Detected out edge: (2, 2, 2) -> (3, 2, 2) 
Detected out edge: (2, 2, 2) -> (2, 1, 2) 
Detected out edge: (2, 2, 2) -> (2, 3, 2) 
Detected out edge: (2, 2, 2) -> (2, 2, 1) 
Detected out edge: (2, 2, 2) -> (2, 2, 3) 
---- 
Detected in edge: (1, 0, 0) -> (0, 0, 0) 
Detected in edge: (0, 1, 0) -> (0, 0, 0) 
Detected in edge: (0, 0, 1) -> (0, 0, 0) 
Detected out edge: (0, 0, 0) -> (1, 0, 0) 
Detected out edge: (0, 0, 0) -> (0, 1, 0) 
Detected out edge: (0, 0, 0) -> (0, 0, 1)