How to find if a vertex exists in a boost graph?

Question

I have a boost graph (with bundled properties). I want to find if a vertex with a certain value already exists in the graph or not. Can someone help me with this? Here, I present a MWE of my existing code:

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#include <iostream>
#include <string>
#include <vector>
#include <boost/graph/adjacency_list.hpp>

struct mytuple
{
    int e1;
    int e2;
    int s;

    bool operator==(const mytuple& a) const
    {
        return ((e1 == a.e1) && (e2 == a.e2) && (s == a.s));
    }
};

struct MyVertex {
    std::string comments;
    int field1;
    mytuple value;
    MyVertex(std::string comments = std::string()) : comments(comments) {}
};

struct MyEdge {
    std::string label;
    MyEdge(std::string label = std::string()) : label(label) {}
};

// Define the graph with the vertex as a mytuple and the vertices container as a vector
using MyTree = boost::adjacency_list<boost::vecS, boost::vecS, boost::bidirectionalS, MyVertex, MyEdge>;
using Vertex = boost::graph_traits<MyTree>::vertex_descriptor; // Define Vertex
using VertexItr = boost::graph_traits<MyTree>::vertex_iterator; // Define Vertex iterator
using Edge = std::pair<boost::graph_traits<MyTree>::edge_descriptor, bool>; // Define Edge
using EdgeItr = boost::graph_traits<MyTree>::edge_iterator; // Define Edge Iterator

int main()
{
    MyTree mytree;

    Vertex v1 = boost::add_vertex(mytree);
    mytree[v1].value = {1, 1, 1};

    Vertex v2 = boost::add_vertex(mytree);
    mytree[v2].value = {2, 2, 2};

    Vertex v3 = boost::add_vertex(mytree);
    mytree[v3].value = {3, 3, 3};

    // Perhaps add some edges

    std::cout << "I want to find if my graph has a vertex containing the value {1, 1, 1}";
    // mytree.findvertex(with value {1, 1, 1})
}

Answer 1

#include <iostream>
#include <string>
#include <vector>
#include <boost/graph/adjacency_list.hpp>


struct mytuple
{
    int e1;
    int e2;
    int s;

    bool operator==(const mytuple& a) const
    {
        return ((e1 == a.e1) && (e2 == a.e2) && (s == a.s));
    }
};

struct MyVertex {
    std::string comments;
    int field1;
    mytuple value;
    MyVertex(std::string comments = std::string()) : comments(comments) {}
};

struct MyEdge {
    std::string label;
    MyEdge(std::string label = std::string()) : label(label) {}
};

// Define the graph with the vertex as a mytuple and the vertices container as a vector
using MyTree = boost::adjacency_list<boost::vecS, boost::vecS, boost::bidirectionalS, MyVertex, MyEdge>;
using Vertex = boost::graph_traits<MyTree>::vertex_descriptor; // Define Vertex
using VertexItr = boost::graph_traits<MyTree>::vertex_iterator; // Define Vertex iterator
using Edge = std::pair<boost::graph_traits<MyTree>::edge_descriptor, bool>; // Define Edge
using EdgeItr = boost::graph_traits<MyTree>::edge_iterator; // Define Edge Iterator

VertexItr findvertex(const MyTree& g, const mytuple& value){
    VertexItr vi, vi_end;
    for (boost::tie(vi, vi_end) = vertices(g); vi != vi_end; ++vi) {
        if(g[*vi].value == value) return vi;
    }
    return vi_end;
}

int main()
{
    MyTree mytree;

    Vertex v1 = boost::add_vertex(mytree);
    mytree[v1].value = {1, 1, 1};
    mytree[v1].comments = "I am the one you seek";

    Vertex v2 = boost::add_vertex(mytree);
    mytree[v2].value = {2, 2, 2};

    Vertex v3 = boost::add_vertex(mytree);
    mytree[v3].value = {3, 3, 3};

    // Perhaps add some edges

    std::cout << "I want to find if my graph has a vertex containing the value {1, 1, 1}\n";
    mytuple tuple = { 1,1,1};
    const auto iter = findvertex(mytree, tuple);
    const auto theEnd = boost::vertices(mytree).second;
    if(iter != theEnd){
    std::cout << "'ere I be: " << mytree[*iter].comments << '\n';
    }
    else{
        std::cout << "failed to find tuple\n";
    }
}

compiled with g++ graph.cpp -std=c++11 -o graph.o -l boost_graph produces the ouput

I want to find if my graph has a vertex containing the value {1, 1, 1}
'ere I be: I am the one you seek