algorithms-and-data-structures/AlgorithmsAndDataStructures/Algorithms/Graph/Misc/TransitiveClosureFloydWarshall.cs at master · arst/algorithms-and-data-structures · GitHub

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using System;
using AlgorithmsAndDataStructures.Algorithms.Graph.Common;

namespace AlgorithmsAndDataStructures.Algorithms.Graph.Misc;

public class TransitiveClosureFloydWarshall
{
#pragma warning disable CA1822 // Mark members as static
    public bool[][] GetReachabilityMatrix(WeightedGraphVertex[] graph)
#pragma warning restore CA1822 // Mark members as static
    {
        if (graph is null) return Array.Empty<bool[]>();

        var reachabillityMatrix = new bool[graph.Length][];

        for (var i = 0; i < reachabillityMatrix.Length; i++)
        {
            reachabillityMatrix[i] = new bool[graph.Length];
            reachabillityMatrix[i][i] = true;

            for (var j = 0; j < graph[i].Edges.Count; j++)
            {
                var edge = graph[i].Edges[j];
                reachabillityMatrix[i][edge.To] = true;
            }
        }


        for (var i = 0; i < graph.Length; i++)
        for (var j = 0; j < graph.Length; j++)
        for (var k = 0; k < graph.Length; k++)
        {
            var isReachableThroughCurrentlyInspectedVertex = reachabillityMatrix[i][k] && reachabillityMatrix[k][j];
            if (isReachableThroughCurrentlyInspectedVertex) reachabillityMatrix[i][j] = true;
        }

        return reachabillityMatrix;
    }
}