/// <summary>
/// Implementacja algorytmu Johnsona, korzysta z algorytmow Bellmana-Forda i Dijkstry
/// </summary>
/// <param name="g"></param> Musi to byc graf skierowany ktory ma juz randomowe wagi i musi byc on spojny(WAŻNE)!!!!
/// Mozna np stworzyc graf skierowany, wydobyc z niego skladowa maksymalnie spojna i nadać jej randomowe wagi
/// <returns></returns> Macierz odleglosci miedzy wszystkimi wierzcholkami
public static int[,] Johnson(DirectedGraphMatrix graph)
{
try
{
int nodes = graph.NodesNr;
int[,] distances = new int[nodes, nodes];
int[] d = new int[nodes];
const int INF = int.MaxValue - 10000;
int[,] wagi = new int[nodes, nodes];
int q = nodes + 1;
int[,] new_connect = new int[q, q];
for (int i = 0; i < nodes; ++i)
{
for (int j = 0; j < nodes; ++j)
{
new_connect[i, j] = graph.getConnect(i, j);
wagi[i, j] = graph.getWeight(i, j);
}
}
DirectedGraphMatrix dgraph = new DirectedGraphMatrix(q, new_connect);
for (int i = 0; i < q - 1; ++i)
{
dgraph.MakeConnection(q - 1, i, 0);
dgraph.setWeight(i, q - 1, INF);
for (int j = 0; j < q - 1; ++j)
{
dgraph.setWeight(i, j, graph.getWeight(i, j));
}
}
List <List <int> > bellman = new List <List <int> >();
for (int i = 0; i < nodes; ++i)
{
bellman.Add(BellmanFord(dgraph, q - 1, i));
d[i] = pathWeight(dgraph, bellman[i]);
if (ujemnyCykl(graph, wagi))
{
throw new Exception("Algorytm Johnsona zostal zatrzymany.");
}
}
for (int i = 0; i < q - 1; ++i)
{
for (int j = 0; j < q - 1; ++j)
{
if (dgraph.GetConnection(i, j))
{
dgraph.setWeight(i, j, dgraph.getWeight(i, j) + d[i] - d[j]);
}
}
}
int[,] last_connect = new int[nodes, nodes];
for (int i = 0; i < nodes; ++i)
{
for (int j = 0; j < nodes; ++j)
{
last_connect[i, j] = dgraph.getConnect(i, j);
}
}
DirectedGraphMatrix lgraph = new DirectedGraphMatrix(nodes, last_connect);
for (int i = 0; i < nodes; ++i)
{
for (int j = 0; j < nodes; ++j)
{
lgraph.setWeight(i, j, dgraph.getWeight(i, j));
}
}
distances = distancesDirectedMatrix(lgraph);
for (int i = 0; i < nodes; ++i)
{
for (int j = 0; j < nodes; ++j)
{
distances[i, j] = distances[i, j] - d[i] + d[j];
}
}
return(distances);
}
catch (Exception)
{
Console.WriteLine("Algorytm Johnsona zatrzymany z powodu ujemnego cyklu w grafie.");
return(new int[5, 5]);
}
}