Question

我刚开始学习如何编程并一直关注此tutorial on graphs，但我使用给定的

遇到了一些问题

AddDirectedEdge(GraphNode<T> from, GraphNode<T> to, int cost)

使用教程中的默认值无法构建，例如

web.AddDirectedEdge("People.aspx", "Privacy.htm");  // People -> Privacy

这给出了错误＆＃34;方法＆＃39; AddDirectedEdge＆＃39;需要2个参数＆＃34; 。添加一个整数作为第三个参数也没有帮助，它只是给出了另一个错误＆＃34;参数＃：无法转换为＆＃39; string＆＃39; to＆＃39; GraphTest.GraphNode＆lt;串GT;＆＃39;＆＃34;

我不确定如何解决此问题，任何有关它的帮助/见解将不胜感激。为便于查看，图形和图形节点类如下所示（这些也可通过上述链接获得）：

 public class GraphNode<T> : Node<T>
{
    private List<int> costs;

    public GraphNode() : base() { }
    public GraphNode(T value) : base(value) { }
    public GraphNode(T value, NodeList<T> neighbors) : base(value, neighbors) { }

    new public NodeList<T> Neighbors
    {
        get
        {
            if (base.Neighbors == null)
                base.Neighbors = new NodeList<T>();

            return base.Neighbors;
        }
    }

    public List<int> Costs
    {
        get
        {
            if (costs == null)
                costs = new List<int>();

            return costs;
        }
    }
}

 public class Graph<T> : IEnumerable<T>
{
    private NodeList<T> nodeSet;

    public Graph() : this(null) { }
    public Graph(NodeList<T> nodeSet)
    {
        if (nodeSet == null)
            this.nodeSet = new NodeList<T>();
        else
            this.nodeSet = nodeSet;
    }

    public void AddNode(GraphNode<T> node)
    {
        // adds a node to the graph
        nodeSet.Add(node);
    }

    public void AddNode(T value)
    {
        // adds a node to the graph
        nodeSet.Add(new GraphNode<T>(value));
    }

    public void AddDirectedEdge(GraphNode<T> from, GraphNode<T> to, int cost)
    {
        from.Neighbors.Add(to);
        from.Costs.Add(cost);
    }

    public void AddUndirectedEdge(GraphNode<T> from, GraphNode<T> to, int cost)
    {
        from.Neighbors.Add(to);
        from.Costs.Add(cost);

        to.Neighbors.Add(from);
        to.Costs.Add(cost);
    }

    public bool Contains(T value)
    {
        return nodeSet.FindByValue(value) != null;
    }

    public bool Remove(T value)
    {
        // first remove the node from the nodeset
        GraphNode<T> nodeToRemove = (GraphNode<T>)nodeSet.FindByValue(value);
        if (nodeToRemove == null)
            // node wasn't found
            return false;

        // otherwise, the node was found
        nodeSet.Remove(nodeToRemove);

        // enumerate through each node in the nodeSet, removing edges to this node
        foreach (GraphNode<T> gnode in nodeSet)
        {
            int index = gnode.Neighbors.IndexOf(nodeToRemove);
            if (index != -1)
            {
                // remove the reference to the node and associated cost
                gnode.Neighbors.RemoveAt(index);
                gnode.Costs.RemoveAt(index);
            }
        }

        return true;
    }

    public NodeList<T> Nodes
    {
        get
        {
            return nodeSet;
        }
    }

    public int Count
    {
        get { return nodeSet.Count; }
    }

    public IEnumerator<T> GetEnumerator()
    {
        throw new NotImplementedException();
    }

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
    {
        throw new NotImplementedException();
    }

    IEnumerator<T> IEnumerable<T>.GetEnumerator()
    {
        throw new NotImplementedException();
    }
}

Answer 1

嗯，显然它抱怨类型不匹配：

您提供string类型而不是GraphNode<T>。

相反，你应该把它称为：

web.AddDirectedEdge(new GraphNode("People.aspx"), new GraphNode("Privacy.htm"), 1);

其中1是费用，是必需的，或

var ppl = new GraphNode("People.aspx");
var prv = new GraphNode("Privacy.htm");
web.AddDirectedEdge(ppl, prv, 1);

如果您希望在代码中进一步重用节点。

作为旁注，似乎你正在犯一些微不足道的错误。在进一步说明之前，我强烈建议您至少参加C＃的基础课程。网上有大量免费提供，this for example。

图数据结构C＃的麻烦

1 个答案: