我的图类基本上由值和map之间的Vertices组成,其中每个Vertex都是其自身的类。每个顶点都有一个值和一个邻接表,将其实现为相邻map和边缘权重之间的Vertices。我正在尝试显示图形中的每个顶点以及与之相邻的顶点,以及将其连接到其相邻顶点的边缘的权重。 (对不起所有代码)

template <class VertexType>
void Graph<VertexType>::display() const
{
    typedef map<VertexType, Vertex<VertexType> >::iterator vertices_iter;
    typedef map<Vertex<VertexType>, int>::iterator adjList_iter;

    for ( vertices_iter v_iter = vertices.begin(); v_iter != vertices.end(); v_iter++ )
    {
        cout << "Vertex: " << v_iter->second.value << endl;
        cout << setw(25) << left << "Adjacent to: " << "Edge weight:\n";
        for ( adjList_iter a_iter = vertices[v_iter->first].adjList.begin(); a_iter != vertices[v_iter->first].adjList.end(); a_iter++ )
            cout <<  "    " << a_iter->first.value << "                         " << a_iter->second << endl;
        cout << endl;
    }
}

但是我收到以下错误:

错误1:
error C2440: 'initializing' : cannot convert from 'std::_Tree_const_iterator<_Mytree>' to 'std::_Tree_iterator<_Mytree>'
1>          with
1>          [
1>              _Mytree=std::_Tree_val<std::_Tmap_traits<unsigned int,Vertex<unsigned int>,std::less<unsigned int>,std::allocator<std::pair<const unsigned int,Vertex<unsigned int>>>,false>>
1>          ]
1>          No constructor could take the source type, or constructor overload resolution was ambiguous
1>          c:\users\user\desktop\cs m20a\topic g project 2\topic g project 2\graph.h(241) : while compiling class template member function 'void Graph<VertexType>::display(void) const'
1>          with
1>          [
1>              VertexType=unsigned int
1>          ]

错误2:
error C2678: binary '[' : no operator found which takes a left-hand operand of type 'const std::map<_Kty,_Ty>' (or there is no acceptable conversion)
1>          with
1>          [
1>              _Kty=unsigned int,
1>              _Ty=Vertex<unsigned int>
1>          ]
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\map(164): could be 'Vertex<VertexType> &std::map<_Kty,_Ty>::operator [](unsigned int &&)'
1>          with
1>          [
1>              VertexType=unsigned int,
1>              _Kty=unsigned int,
1>              _Ty=Vertex<unsigned int>
1>          ]
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\map(209): or       'Vertex<VertexType> &std::map<_Kty,_Ty>::operator [](const unsigned int &)'
1>          with
1>          [
1>              VertexType=unsigned int,
1>              _Kty=unsigned int,
1>              _Ty=Vertex<unsigned int>
1>          ]
1>          while trying to match the argument list '(const std::map<_Kty,_Ty>, const unsigned int)'
1>          with
1>          [
1>              _Kty=unsigned int,
1>              _Ty=Vertex<unsigned int>
1>          ]

这是我的Graph类,如果有帮助的话。
template <class VertexType>
class Graph
{
private:
     // list of all vertices in the graph. assumes non-duplicate data.
    map< VertexType, Vertex<VertexType> > vertices;

    const unsigned MAX_VERTICES;  // Maximum number of vertices the graph can hold.
    unsigned numVertices;         /** Current number of vertices in the graph. */
    unsigned numEdges;            /** Number of edges in the graph. */

    typename map<VertexType, int>::iterator findEdge( const VertexType& v, const VertexType& w ) const;

public:
   Graph( unsigned max );

   unsigned getNumVertices() const;
   unsigned getMaxNumVertices() const;
   unsigned getNumEdges() const;
   int getWeight( const VertexType& v, const VertexType& w ) const;

   Graph<VertexType>& addVertex( const VertexType& newValue );
   Graph<VertexType>& addEdge( const VertexType& v, const VertexType& w, int weight );
   void removeEdge( const VertexType& v, const VertexType& w );
   void BFS( const VertexType& v ) const;
   void display() const;
}; // end Graph

最佳答案

您将方法声明为const,也就是说,它不会更改任何成员变量:

void Graph<VertexType>::display() const

这意味着您只能使用底层成员变量的const方法;因此,您的基础类型为const_iterator:
typedef map<VertexType, Vertex<VertexType> >::const_iterator vertices_iter;
typedef map<Vertex<VertexType>, int>::const_iterator adjList_iter;

更好的是,如果您使用的是C++11,请利用auto

至于第二个错误,我看不到是什么原因,但是,您无缘无故地进行查找工作:
for(auto a_iter = vertices[v_iter->first].adjList.begin();
    a_iter != vertices[v_iter->first].adjList.end();
    a_iter++ )

假设v_iter是原始循环中的vertices.begin()。那么vertices[v_iter->first]实际上与*v.begin()相同。您可以将其替换为:
for(auto a_iter = v_iter->first.adjList.begin();
    a_iter != v_iter->first.adjList.end();
    a_iter++ )

07-24 09:38
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