通过与输入相同的提升图创建无向图
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【中文标题】通过与输入相同的提升图创建无向图【英文标题】:Create undirected graph by boost graph same as the input 【发布时间】:2014-06-01 10:55:30 【问题描述】:我想创建如下图,第一列是顶点,其他的是邻接顶点
1 2 3 4 7 2 1 3 4 3 1 2 4 4 1 2 3 5 5 4 6 7 8 6 5 7 8 7 1 5 6 8 8 5 6 7我像这样将边添加到图中
using MinCutG = boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS>;
MinCutG graph;
std::vector<std::vector<int> > input 1,2,3,4,7, 2,1,3,4, 3,1,2,4,
4,1,2,3,5, 5,4,6,7,8, 6,5,7,8, 7,1,5,6,8, 8,5,6,7;
for(auto const &data : input)
auto begin = std::begin(data);
auto end = std::end(data);
if(begin != end)
auto const Vertex = *begin;
++begin;
while(begin != end)
boost::add_edge(Vertex, *begin, graph);
++begin;
打印图表
template<typename Graph>
void print_adjacent_vertex(Graph const &g)
for (auto vertex = vertices(g); vertex.first != vertex.second; ++vertex.first)
std::cout << *vertex.first << " is connected with ";
for (auto neighbour = adjacent_vertices(*vertex.first, g);
neighbour.first != neighbour.second; ++neighbour.first)
std::cout << *neighbour.first << " ";
std::cout<<std::endl;
我希望输出应该与输入相同,但事实并非如此 结果是
1 与 2 3 4 7 2 3 4 7 相连 2与1 1 3 4 3 4相连 3与1 2 1 2 4 4相连 4与1 2 3 1 2 3 5 5相连 5与4 4 6 7 8 6 7 8相连 6与5 5 7 8 7 8相连 7与1 5 6 1 5 6 8 8相连 8与5 6 7 5 6 7相连我的预期结果
1与2 3 4 7相连 2与1 3 4相连 3与1 2 4相连 4与1 2 3 5相连 5与4 6 7 8相连 6与6 5 7 8相连 7 与 7 1 5 6 8 相连 8 与 8 5 6 7 相连【问题讨论】:
【参考方案1】:简而言之,将setS
用于OutEdgeList
模板参数将禁用平行边,从而产生所需的输出。
boost::adjacency_list
的第一个模板参数是OutEdgeList
,它控制某些图形行为,例如允许或禁止平行边。在无向MinCutG
图的情况下,vecS
用作OutEdgeList
,这将启用平行边。例如,如果一个无向图支持平行边,那么:
add_edge(1, 2, graph); // Vertex 1 and 2 are adjacent to one another via edge A.
add_edge(2, 1, graph); // Vertex 1 and 2 are adjacent to one another via edge B,
// which is parallel to edge A.
顶点1
的adjacent_vertices()
将包含两次顶点2
,每条边一次(A
和B
)。
如documentation 中所述,可以通过对OutEdgeList
使用setS
或hash_setS
选择器来禁用平行边。例如,改变:
using MinCutG = boost::adjacency_list<
boost::vecS, // OutEdgeList with parallel edges
boost::vecS,
boost::undirectedS>;
到:
using MinCutG = boost::adjacency_list<
boost::setS, // OutEdgeList with no parallel edges
boost::vecS,
boost::undirectedS>;
这是一个使用原始代码的example,只是将OutEdgeList
从vecS
更改为setS
:
#include <iostream>
#include <vector>
#include <boost/graph/adjacency_list.hpp>
template<typename Graph>
void print_adjacent_vertex(Graph const &g)
for (auto vertex = vertices(g); vertex.first != vertex.second;
++vertex.first)
std::cout << *vertex.first << " is connected with ";
for (auto neighbour = adjacent_vertices(*vertex.first, g);
neighbour.first != neighbour.second; ++neighbour.first)
std::cout << *neighbour.first << " ";
std::cout<<std::endl;
int main()
using MinCutG = boost::adjacency_list<
boost::setS, boost::vecS, boost::undirectedS>;
MinCutG graph;
std::vector<std::vector<int> > input
1,2,3,4,7,
2,1,3,4,
3,1,2,4,
4,1,2,3,5,
5,4,6,7,8,
6,5,7,8,
7,1,5,6,8,
8,5,6,7
;
for(auto const &data : input)
auto begin = std::begin(data);
auto end = std::end(data);
if(begin != end)
auto const Vertex = *begin;
++begin;
while(begin != end)
boost::add_edge(Vertex, *begin, graph);
++begin;
print_adjacent_vertex(graph);
产生以下输出:
0 is connected with
1 is connected with 2 3 4 7
2 is connected with 1 3 4
3 is connected with 1 2 4
4 is connected with 1 2 3 5
5 is connected with 4 6 7 8
6 is connected with 5 7 8
7 is connected with 1 5 6 8
8 is connected with 5 6 7
【讨论】:
【参考方案2】:正如 Tanner 解释的那样,您基本上将每条边添加两次,首先是 (a,b),然后是 (b,a)。避免这种情况的一种但相当昂贵的方法是使用setS
作为控制边缘容器的模板参数。这就是 Tanner 在他的回答中提出的建议。
另一种方法是在添加之前检查边缘是否存在。这意味着线
boost::add_edge(Vertex, *begin, graph);
应该替换为
if (! edge(Vertex, *begin, graph).second ) //edge does not exist yet
boost::add_edge(Vertex, *begin, graph);
在大多数情况下,此代码可能会更快并消耗更少的内存。
【讨论】:
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