读取文本文件并从中创建多维数组

Question

我想读取一个txt文件并创建一个多维int数组，格式如下：

var graph = new[,]
    {
        // 0   1   2   3   4   5   6   7   8   9  10  11...n
        { 0,  0,  0,  0,  0,  0, 10,  0, 12,  0,  0,  0 }, // 0
        { 0,  0,  0,  0, 20,  0,  0, 26,  0,  5,  0,  6 }, // 1
        { 0,  0,  0,  0,  0,  0,  0, 15, 14,  0,  0,  9 }, // 2
        { 0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  7,  0 }, // 3
        { 0, 20,  0,  0,  0,  5, 17,  0,  0,  0,  0, 11 }, // 4
        { 0,  0,  0,  0,  5,  0,  6,  0,  3,  0,  0, 33 }, // 5
        {10,  0,  0,  0, 17,  6,  0,  0,  0,  0,  0,  0 }, // 6
        { 0, 26, 15,  0,  0,  0,  0,  0,  0,  3,  0, 20 }, // 7
        {12,  0, 14,  0,  0,  3,  0,  0,  0,  0,  0,  0 }, // 8
        { 0,  5,  0,  0,  0,  0,  0,  3,  0,  0,  0,  0 }, // 9
        { 0,  0,  0,  7,  0,  0,  0,  0,  0,  0,  0,  0 }, // 10
        { 0,  6,  9,  0, 11, 33,  0, 20,  0,  0,  0,  0 }, // 11..n
  };

这应该表示图中的节点以及彼此之间的距离。我的 txt 文件看起来像这样（图片和图形值不匹配）：

第一个值是开始节点，第二个值是结束节点，第三个值应该是距离。 所以表中行的索引是现有的起始节点，如果节点之间没有直接连接，则字段中的值应该是0，或者如果存在直接连接，它应该与txt文件有距离。列的索引应该是所有的结束节点。

我是这样开始的：

 using (var reader = new StreamReader(@"USA-road-d.CAL.gr"))
    {
        while (!reader.EndOfStream)
        {
            var lineCount = File.ReadLines(@"USA-road-d.CAL.gr").Count();
            var pre_graph = new int[lineCount];

            //initialize array with 0s
            Array.Clear(pre_graph, 0, pre_graph.Length);

            string new_line;

            while ((new_line = reader.ReadLine()) != null)
            {
                var values = new_line.Split(null);
                pre_graph[int.Parse(values[2])] = int.Parse(values[3]);
            }
        }
    }

var pre_graph = new int[lineCount]; 是错误的，因为有多个边。我只想将不同起始节点的计数作为数组长度。

我不知道如何得到这个。有人可以帮忙吗？

最后我想用这个图来实现 dijkstra 算法：

using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;

public static class DijkstraWithoutQueue
{
    public static List<int> DijkstraAlgorithm(int[,] graph, int sourceNode, int destinationNode)
    {
        var n = graph.GetLength(0);

        var distance = new int[n];
        for (int i = 0; i < n; i++)
        {
            distance[i] = int.MaxValue;
        }

        distance[sourceNode] = 0;

        var used = new bool[n];
        var previous = new int?[n];

        while (true)
        {
            var minDistance = int.MaxValue;
            var minNode = 0;
            for (int i = 0; i < n; i++)
            {
                if (!used[i] && minDistance > distance[i])
                {
                    minDistance = distance[i];
                    minNode = i;
                }
            }

            if (minDistance == int.MaxValue)
            {
                break;
            }

            used[minNode] = true;

            for (int i = 0; i < n; i++)
            {
                if (graph[minNode, i] > 0)
                {
                    var shortestToMinNode = distance[minNode];
                    var distanceToNextNode = graph[minNode, i];

                    var totalDistance = shortestToMinNode + distanceToNextNode;

                    if (totalDistance < distance[i])
                    {
                        distance[i] = totalDistance;
                        previous[i] = minNode;
                    }
                }
            }
        }

        if (distance[destinationNode] == int.MaxValue)
        {
            return null;
        }

        var path = new LinkedList<int>();
        int? currentNode = destinationNode;
        while (currentNode != null)
        {
            path.AddFirst(currentNode.Value);
            currentNode = previous[currentNode.Value];
        }

        return path.ToList();
    }

    public static void Main()
    {


        var graph = new[,]
        {
            // 0   1   2   3   4   5   6   7   8   9  10  11
            { 0,  0,  0,  0,  0,  0, 10,  0, 12,  0,  0,  0 }, // 0
            { 0,  0,  0,  0, 20,  0,  0, 26,  0,  5,  0,  6 }, // 1
            { 0,  0,  0,  0,  0,  0,  0, 15, 14,  0,  0,  9 }, // 2
            { 0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  7,  0 }, // 3
            { 0, 20,  0,  0,  0,  5, 17,  0,  0,  0,  0, 11 }, // 4
            { 0,  0,  0,  0,  5,  0,  6,  0,  3,  0,  0, 33 }, // 5
            {10,  0,  0,  0, 17,  6,  0,  0,  0,  0,  0,  0 }, // 6
            { 0, 26, 15,  0,  0,  0,  0,  0,  0,  3,  0, 20 }, // 7
            {12,  0, 14,  0,  0,  3,  0,  0,  0,  0,  0,  0 }, // 8
            { 0,  5,  0,  0,  0,  0,  0,  3,  0,  0,  0,  0 }, // 9
            { 0,  0,  0,  7,  0,  0,  0,  0,  0,  0,  0,  0 }, // 10
            { 0,  6,  9,  0, 11, 33,  0, 20,  0,  0,  0,  0 }, // 11
        };

        PrintPath(graph, 0, 2);
        PrintPath(graph, 0, 10);
        PrintPath(graph, 0, 11);
        PrintPath(graph, 0, 1);
    }

    public static void PrintPath(int[,] graph, int sourceNode, int destinationNode)
    {
        Console.Write(
            "Shortest path [{0} -> {1}]: ",
            sourceNode,
            destinationNode);

        var path = DijkstraWithoutQueue.DijkstraAlgorithm(graph, sourceNode, destinationNode);

        if (path == null)
        {
            Console.WriteLine("no path");
        }
        else
        {
            int pathLength = 0;
            for (int i = 0; i < path.Count - 1; i++)
            {
                pathLength += graph[path[i], path[i + 1]];
            }

            var formattedPath = string.Join("->", path);
            Console.WriteLine("{0} (length {1})", formattedPath, pathLength);
        }
    }
    }

Answer 1

我在 GitHub 上为你准备了一个解决方案，

1890815x1890815矩阵的数组上网不是个好主意。 表示这样一个数组 (1890815x1890815x4x2) 大约需要 28 601 450 MB，或者您需要使用 28 PB 内存的解决方案。

我想您将永远无法为美国路线图创建实体矩阵，因为您可能需要大约 1T 的 DDR 内存（经过优化）或 28 PB（包括零），我为您准备了 Visual Studio 解决方案（VS2019 预览版）需要打开项目）：

• https://github.com/hack2root/read-matrix

这是一个好消息，如果忘记了 28 PB 的要求，您可以创建和使用连接矩阵 (C# 8.0) 从文件加载数据并在大约 5 秒内创建节点和边的树结构。

5.6 秒从内存中的存档加载所有美国道路，并验证结构

    static class Program
    {
        static async Task Main(string[] args)
        {
            using (var archive = ZipFile.OpenRead(args[0]))
            {
                var entry = archive.Entries.Where(_ => _.FullName.Equals("USA-road-d.CAL.gr", StringComparison.OrdinalIgnoreCase)).FirstOrDefault();
                if (entry != null)
                {
                    var stopwatch = new Stopwatch();
                    stopwatch.Start();
                    var data = new List<string>(Decompress(entry.Open()));
                    var graph = new Graph(data);
                    stopwatch.Watch();
                    Console.ReadLine();
                }
            }
        }

        public static IEnumerable<string> Decompress(Stream stream)
        {
            using (var reader = new StreamReader(stream, Encoding.ASCII))
            {
                string line;
                while ((line = reader.ReadLine()) != null)
                {
                    yield return line;
                }
            }
        }

        public class Edge
        {
            public Edge(Graph graph, Node v1, Node v2, int distance, bool isDirectional = false)
            {
                Graph = graph;
                V1 = v1;
                V2 = v2;
                Distance = distance;
                v1.AddEdge(this);
                if (!IsDirectional)
                    v2.AddEdge(this);
            }
            internal Graph Graph { get; }
            public Node V1 { get; }
            public Node V2 { get; }
            public int Distance { get; }
            public bool IsDirectional { get; }
        }

        public class Node
        {
            static int counter = 0;
            readonly List<Edge> _edges = new List<Edge>();
            public Node(Graph graph, int index)
            {
                Graph = graph;
                Index = index;
                Number = counter++;
            }
            internal Graph Graph { get; }
            public int Index { get; }
            public int Number { get; }
            public IEnumerable<Edge> Edges => _edges;
            public void AddEdge(Edge edge) => _edges.Add(edge);
        }

        public class Graph
        {
            Dictionary<int, Node> _nodes { get; } = new Dictionary<int, Node>();
            readonly Parameters _parameters;
            readonly List<Edge> _edges;
            readonly List<string> _comments;
            public IParameters Parameters => _parameters;
            public IEnumerable<Edge> Edges => _edges;
            public IEnumerable<string> Comments => _comments;
            public Node GetNode(int index) => _nodes.ContainsKey(index) ? _nodes[index] : (_nodes[index] = new Node(this, index));
            public Graph(IEnumerable<string> lines, bool isDirectional = false)
            {
                IEnumerable<string> parameters = new List<string>(lines.Where(_ => _[0] == 'p'));
                IEnumerable<string> edges = new List<string>(lines.Where(_ => _[0] == 'a'));
                IEnumerable<string> comments = new List<string>(lines.Where(_ => _[0] == 'c'));
                _parameters = 
                    parameters
                    .Select(_ => _.Split(' '))
                    .Select(_ => _[1] == "sp" ? new Parameters(int.Parse(_[2]), int.Parse(_[3])) : null).FirstOrDefault();
                _edges =
                    edges
                    .Select(_ => _.Split(' '))
                    .Select(_ => new Edge(this, GetNode(int.Parse(_[1])), GetNode(int.Parse(_[2])), int.Parse(_[3]), isDirectional))
                    .ToList();
                _comments =
                    comments
                    .Select(_ => _.Substring(1)).ToList();
                if (_parameters.Nodes != _nodes.Keys.Count)
                {
                    throw new Exception("invalid nodes count");
                }
                if (_parameters.Edges != _edges.Count)
                {
                    throw new Exception("invalid edges count");
                }
            }
        }

        public interface IParameters
        {
            int Nodes { get; }
            int Edges { get; }
        }
        public class Parameters: IParameters
        {
            public int Nodes { get; }
            public int Edges { get; }
            public Parameters(int nodes, int edges)
            {
                Nodes = nodes;
                Edges = edges;
            }
        }

    }

    public static class StopwatchExtensions
    {
        public static void Watch(this Stopwatch stopwatch, string message = "",
        [CallerMemberName] string memberName = "",
        [CallerFilePath] string sourceFilePath = "",
        [CallerLineNumber] int sourceLineNumber = 0) =>
        Console.WriteLine(
            $"{stopwatch.Elapsed} " +
            $"{message} " +
            $"{memberName} " +
            $"{sourceFilePath}:{sourceLineNumber}");
    }