gistlib - journey planner in csharp

To create a journey planner in C#, we can use graph algorithms, specifically the Dijkstra algorithm, to find the shortest path between two locations. Here are the basic steps to create a journey planner:

Create a class to represent the graph. Each vertex in the graph should be a location, and each edge should be a road or a path between two locations. Each edge should have a weight representing the travel distance between the two vertices.


main.cs
public class Graph
{
    public class Vertex
    {
        public string Name { get; set; }
    }

    public class Edge
    {
        public Vertex Start { get; set; }
        public Vertex End { get; set; }
        public int Weight { get; set; }
    }

    public List<Vertex> Vertices { get; set; }
    public List<Edge> Edges { get; set; }
}
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Populate the graph with vertices and edges. This can be done manually or by importing data from an external source (e.g. a CSV file).


main.cs
Graph graph = new Graph();
graph.Vertices = new List<Graph.Vertex>()
{
    new Graph.Vertex{ Name = "A" },
    new Graph.Vertex{ Name = "B" },
    new Graph.Vertex{ Name = "C" },
    new Graph.Vertex{ Name = "D" }
};

graph.Edges = new List<Graph.Edge>()
{
    new Graph.Edge{ Start = graph.Vertices[0], End = graph.Vertices[1], Weight = 10 },
    new Graph.Edge{ Start = graph.Vertices[1], End = graph.Vertices[2], Weight = 8 },
    new Graph.Edge{ Start = graph.Vertices[2], End = graph.Vertices[3], Weight = 7 },
    new Graph.Edge{ Start = graph.Vertices[0], End = graph.Vertices[3], Weight = 15 },
    new Graph.Edge{ Start = graph.Vertices[0], End = graph.Vertices[2], Weight = 20 }
};
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Implement the Dijkstra algorithm to find the shortest path between two vertices. This algorithm works by starting at the source vertex and visiting the neighboring vertices with the smallest distance. We maintain a priority queue of vertices that need to be visited, sorted by their distance from the source vertex. We also keep track of the distances of each visited vertex.


main.cs
public static List<Graph.Vertex> GetShortestPath(Graph graph, Graph.Vertex source, Graph.Vertex target)
{
    Dictionary<Graph.Vertex, int> distances = new Dictionary<Graph.Vertex, int>();
    Dictionary<Graph.Vertex, Graph.Vertex> parents = new Dictionary<Graph.Vertex, Graph.Vertex>();
    PriorityQueue<Graph.Vertex> queue = new PriorityQueue<Graph.Vertex>();

    foreach (Graph.Vertex vertex in graph.Vertices)
    {
        distances[vertex] = int.MaxValue;
    }

    distances[source] = 0;
    queue.Enqueue(source, 0);

    while (!queue.IsEmpty)
    {
        Graph.Vertex current = queue.Dequeue();

        if (current == target)
        {
            break;
        }

        foreach (Graph.Edge edge in graph.Edges.Where(e => e.Start == current))
        {
            int distance = distances[current] + edge.Weight;

            if (distance < distances[edge.End])
            {
                distances[edge.End] = distance;
                parents[edge.End] = current;

                if (!queue.Contains(edge.End))
                {
                    queue.Enqueue(edge.End, distance);
                }
            }
        }
    }

    List<Graph.Vertex> path = new List<Graph.Vertex>();

    if (!parents.ContainsKey(target))
    {
        return null;
    }

    Graph.Vertex currentVertex = target;

    while (currentVertex != source)
    {
        path.Insert(0, currentVertex);
        currentVertex = parents[currentVertex];
    }

    path.Insert(0, source);

    return path;
}
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Finally, we can call the GetShortestPath method to get the shortest path between two locations. We can then print out the path or perform further calculations based on the result.


main.cs
Graph.Vertex source = graph.Vertices[0];
Graph.Vertex target = graph.Vertices[3];
List<Graph.Vertex> path = GetShortestPath(graph, source, target);

if (path == null)
{
    Console.WriteLine("No path exists.");
}
else
{
    Console.Write("Shortest path: ");

    foreach (Graph.Vertex vertex in path)
    {
        Console.Write("{0} ", vertex.Name);
    }

    Console.WriteLine();
}
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journey planner in csharp

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