triplepai / Dijkstra

Dijkstra algorithm C#

I learn and wrote the code via this link https://www.youtube.com/watch?v=pVfj6mxhdMw

Usage example

        // Intial Graph and add all node
        Graph graph = new Graph();
        graph.AddNode("A");
        graph.AddNode("B");
        graph.AddNode("C");
        graph.AddNode("D");
        graph.AddNode("E");

        // Bind path weight between node
        graph.AddConnection("A", "B", 6);
        graph.AddConnection("A", "D", 1);
        graph.AddConnection("B", "D", 2);
        graph.AddConnection("B", "E", 2);
        graph.AddConnection("B", "C", 5);
        graph.AddConnection("D", "E", 1);
        graph.AddConnection("E", "C", 5);

        DijkstraAlgo algo = new DijkstraAlgo();
        // Let A is start node
        IDictionary<string, NodeRecord> result = algo.CalculateDistances(graph, "A");

        // print all shortest path of each node
        foreach (var item in result)
        {
            Console.WriteLine(item.Key + " shortest path:" + item.Value.lowestWeight + " previous node:" + item.Value.previousNode?.name);
        }

Sample step of Dijkstra algorithm

1. Set up the node and weight of each connection node
2. Create a table to record lowest weight of each node and set lowest weight to infinite except start node = 0
3. Set all node in unvisited list
4. Loop all connected node of current/start node by start at lowest weight connected node first
5. Connected node must not be visited node
6. If table record of this connected node have lowest weight more than current node (weight) + this connected node (weight) then update the lowest weight
7. Set current node to visited node
8. Set next current node by choosing lowest weight connected node of current node
9. If still have unvisited node then goto 4.