1

我的图表类基本上由一个map介于 和 之间的值组成Vertices，其中每个Vertex都是其自身的一个类。每个顶点都有一个值和一个邻接列表，它被实现为map相邻Vertices和边之间的权重。我试图显示图中的每个顶点以及它相邻的顶点以及将其连接到其相邻顶点的边的权重。（对不起所有的代码）

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;
    }
}

但我收到以下错误：

错误一：

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课，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
4

2 回答 2

1

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

这意味着您必须只使用const底层成员变量的方法；因此const_iterators 用于您的基础类型：

typedef map<VertexType, Vertex<VertexType> >::const_iterator vertices_iter;
typedef map<Vertex<VertexType>, int>::const_iterator adjList_iter;

更好的是，如果您正在使用C++11，请使用auto.

至于你的第二个错误，我看不出究竟是什么原因造成的，但是，你正在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++ )

说v_iter是vertices.begin()在原始循环中。那么vertices[v_iter->first]实际上与*v.begin(). 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++ )
于 2013-05-08T07:45:55.447 回答
1

问题是

void Graph<VertexType>::display() const

是一个 const 方法，所以 Graph 的每个成员也是其中的 const。

在这里，您使用非常量迭代器

for ( vertices_iter v_iter = vertices.begin(); v_iter != vertices.end(); v_iter++ )

改用 const 迭代器

typedef map<VertexType, Vertex<VertexType> >::const_iterator vertices_iter;
于 2013-05-08T07:48:14.443 回答