使用迭代器访问数据。升压图

Question

我是 C++ 和 boost 图形库的新手。我正在尝试使用迭代器访问已存储在我的图形 "lattuce" 中的信息，更具体地说，是两个特定节点之间的边的权重。

此数据随后将由 A* 算法（不是 Boost 图中的算法）使用。我也不确定迭代器是否是解决这个问题的方法，所以任何指导或批评将不胜感激。

struct Point {//struct point with vertex properties
    int x, y;
    int parentx, parenty;
    double g;
    double h;
     friend std::ostream& operator<<(std::ostream& os, Point p) {
      return os << "[" << p.x << "," << p.y << "]";
    }
};

int main() {
//declarations
typedef property < edge_weight_t, double >Weight;
using std::vector;//?
using Graph = adjacency_list<setS, vecS, undirectedS, Point, Weight>;//graph includes our created point struct property<edge_weight_t
using vertex_descriptor = Graph::vertex_descriptor;
Graph lattuce;

//lattuce graph is created with weighted edges value 1 or 1,41 if diagonal. The functions used on a loop are:
//add_edge(nodes[p.x][p.y],nodes[neighbour.x][neighbour.y], Weight(1.0), lattuce);
//add_edge(nodes[p.x][p.y],nodes[neighbour.x][neighbour.y], Weight(1.4), lattuce);

如果需要有关生成图表的代码的更多信息，我会提供。谢谢

Answer 1

通过boost::property_map:

可以得到有向图和无向图中的link条边权重

boost::property_map<UndirectedGraph, boost::edge_weight_t>::type EdgeWeightMap = get(boost::edge_weight_t(), g);

下面给出的示例实现首先构建以下简单图（特别是没有循环的树）：

...然后用boost::property_map得到每条边的权值，打印出来：

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

typedef boost::property<boost::edge_weight_t, double> EdgeWeight;
typedef boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS, boost::no_property, EdgeWeight> UndirectedGraph;
typedef boost::graph_traits<UndirectedGraph>::edge_iterator edge_iterator;

int main(int, char*[])
{
    // 1. Undirected graph - print out the edge weights
    UndirectedGraph g;

    boost::add_edge(0, 1, 8, g);
    boost::add_edge(0, 5, 2, g);
    boost::add_edge(5, 6, 1, g);
    boost::add_edge(4, 5, 5, g);
    boost::add_edge(3, 5, 7, g);

    boost::property_map<UndirectedGraph, boost::edge_weight_t>::type EdgeWeightMap = get(boost::edge_weight_t(), g);

    std::pair<edge_iterator, edge_iterator> edgePair;
    for (edgePair = edges(g); edgePair.first != edgePair.second; ++edgePair.first)
    {
        std::cout << *edgePair.first << " " << EdgeWeightMap[*edgePair.first] << std::endl;
    }   

    return 0;
}

给出以下控制台输出，将边显示为（开始，结束）节点对加上它们各自的权重：

使用迭代器访问数据。升压图

Using iterators to access data. Boost graph

c++

boost

graph

a-star