public TopologicalSorting(DirectedWeightedGraph g)
{
int countVertices = g.g.Length;
marked = new bool[countVertices];
for (int v = 0; v < countVertices; v++)
{
Dfs(g, v);
}
}
public TopologicalSorting(DirectedWeightedGraph g)
{
int countVertices = g.g.Length;
marked = new bool[countVertices];
for (int v = 0; v < countVertices; v++)
{
Dfs(g, v);
}
}
public static string[] ShortestPathsInDAG(DirectedWeightedGraph g, int from)
{
// Algorithms by Dasgupta, Papadimitriou, Vazirani. McGraw-Hill. 2006 Chapter 4.7. page 119
int countVerices = g.g.Length;
int[] dist = new int[countVerices];
for (int i = 0; i < dist.Length; i++)
{
dist[i] = Int32.MaxValue / 4;
}
dist[from] = 0;
Algorithms.TopologicalSorting ts = new Algorithms.TopologicalSorting(g);
int[] order = ts.GetResult();
//for (int u = 0; u < a.Length; u++)
//{
// Console.WriteLine(a[u] + " ");
//}
//return new string[1] { "x" };
for (int i = 0; i < order.Length; i++)
{
foreach (var e in g.g[order[i]])
{
if ((dist[order[i]] == Int32.MaxValue / 4) && (dist[e.neighbor] == Int32.MaxValue / 4))
{
continue;
}
dist[e.neighbor] = Math.Min(dist[e.neighbor], dist[order[i]] + e.weight);
}
}
// convert "infinite" to "x"
string[] res = new string[dist.Length];
for (int u = 0; u < countVerices; u++)
{
if (dist[u] == Int32.MaxValue / 4)
{
res[u] = "x";
}
else
{
res[u] = dist[u].ToString();
}
}
return(res);
}
public static string[] ShortestPathsInDAG(DirectedWeightedGraph g, int from)
{
// Algorithms by Dasgupta, Papadimitriou, Vazirani. McGraw-Hill. 2006 Chapter 4.7. page 119
int countVerices = g.g.Length;
int[] dist = new int[countVerices];
for (int i = 0; i < dist.Length; i++)
{
dist[i] = Int32.MaxValue / 4;
}
dist[from] = 0;
Algorithms.TopologicalSorting ts = new Algorithms.TopologicalSorting(g);
int[] order = ts.GetResult();
//for (int u = 0; u < a.Length; u++)
//{
// Console.WriteLine(a[u] + " ");
//}
//return new string[1] { "x" };
for (int i = 0; i < order.Length; i++)
{
foreach (var e in g.g[order[i]])
{
if ((dist[order[i]] == Int32.MaxValue / 4) && (dist[e.neighbor] == Int32.MaxValue / 4))
{
continue;
}
dist[e.neighbor] = Math.Min(dist[e.neighbor], dist[order[i]] + e.weight);
}
}
// convert "infinite" to "x"
string[] res = new string[dist.Length];
for (int u = 0; u < countVerices; u++)
{
if (dist[u] == Int32.MaxValue / 4)
{
res[u] = "x";
}
else
{
res[u] = dist[u].ToString();
}
}
return res;
}
private void Dfs(DirectedWeightedGraph g, int v)
{
if (marked[v])
{
return;
}
marked[v] = true;
foreach (Neighbor n in g.g[v])
{
Dfs(g, n.neighbor);
}
reversePost.Push(v);
}
private void Dfs(DirectedWeightedGraph g, int v)
{
if (marked[v])
{
return;
}
marked[v] = true;
foreach (Neighbor n in g.g[v])
{
Dfs(g, n.neighbor);
}
reversePost.Push(v);
}
static void Main(string[] args)
{
string file = "rosalind_sdag";
DirectedWeightedGraph g = new DirectedWeightedGraph(file + ".txt");
//for (int v = 0; v < g.g.Length; v++)
//{
// Console.Write("{0} : ", v);
// foreach (var n in g.g[v])
// {
// Console.Write("{0} {1}, ", n.neighbor, n.weight);
// }
// Console.WriteLine();
//}
string[] res = Rosalind.ShortestPathsInDAG(g, 0);
Utils.PrintArrayToFile(res, file + ".out.txt");
Utils.Finish();
}
