Question

我有这样的方法：

边缘就像这样

4这是节点计数

1 2 1前两个值是顶点，第三个元素是边的权重

4 1 2

2 3 2

1 3 5

public static List<Tuple<long,long>>[] WeightedGraph(long NodeCount,long[][] edges)
{
    List<Tuple<long, long>>[] Weightedgraph = new List<Tuple<long, long>>[NodeCount + 1];
    for(int i=0; i<Weightedgraph.Length;i++)
    {
        Weightedgraph[i] = new List<Tuple<long, long>>();
    }
    foreach(var vertex in edges)
    {
        **Weightedgraph[vertex[0]].Add();**
    }
}

我如何完成**部分？

Answer 1

最简单的方法是使用Tuple.Create(long, long)：

public static List<Tuple<long, long>>[] WeightedGraph(long NodeCount, long[][] edges)
{
    List<Tuple<long, long>>[] weightedgraph = new List<Tuple<long, long>>[NodeCount + 1];

    for (int i = 0; i < weightedgraph.Length; i++)
    {
        weightedgraph[i] = new List<Tuple<long, long>>();
    }

    foreach (var vertex in edges)
    {
        weightedgraph[vertex[0]].Add(Tuple.Create(1L, 2L));
    }

    return weightedgraph;
}

但是请注意，对于C＃7或更高版本，您可以使用the (x, y) "value tuple" syntax简化操作并为元组元素提供更有意义的名称。

在下面的示例中，我修改了您的代码以调用元组元素X和Y：

public static List<(long X, long Y)>[] WeightedGraph(long nodeCount, long[][] edges)
{
    var weightedgraph = new List<(long X, long Y)>[nodeCount + 1];

    for (int i = 0; i < weightedgraph.Length; i++)
    {
        weightedgraph[i] = new List<(long X, long Y)>();
    }

    foreach (var vertex in edges)
    {
        weightedgraph[vertex[0]].Add((1L, 2L));
    }

    return weightedgraph;
}

Answer 2

让我们添加可读性（该索引表示什么）：

// I've changed NodeCount into int: 
// do you really want a graph with more than 2e9 vertexes?
public static List<Tuple<long,long>>[] WeightedGraph(int NodeCount, long[][] edges) {
  //TODO: validate NodeCount and edges

  // Naming: "WeightedGraph" is the method's name; "result" is what we return 
  // Initialization: we want
  List<Tuple<long, long>>[] result = Enumerable
    .Range(0, NodeCount)                            // NodeCount vertexes
    .Select(node => new List<Tuple<long, long>>())  //   Each has a List<T> of edges
    .ToArray();                                     // Organized as an array

  foreach (var edge in edges) {
    // Let's add readability end decrypt edges format
    int vertexFrom = (int) (edge[0]);
    long vertexTo = edge[1];
    long edgeWeight = edge[2];

    result[vertexFrom].Add(Tuple.Create(vertexTo, edgeWeight)); 
  }  

  return result;
}

如何在C＃中使用List <tuple <long，long >> []？

2 个答案: