public static PathStats ShortestPath(DirectedGraph g, int s)
{
#region Initialization
var stats = new PathStats(g.V);
for (var i = 0; i < stats.Dist.Length; i++)
{
stats.Dist[i] = int.MaxValue;
stats.Prev[i] = -1;
}
stats.Dist[s] = 0;
#endregion
var dfsStats = Dfs.DepthFirstSearch(g);
var linearization = dfsStats.Linearization;
Debug.WriteLine(dfsStats);
foreach (var u in linearization)
{
foreach (var v in g.Adjacent(u))
{
if (stats.Dist[v.V2] > stats.Dist[v.V1] + v.Weight)
{
stats.Dist[v.V2] = stats.Dist[v.V1] + v.Weight;
stats.Prev[v.V2] = u;
}
}
}
return stats;
}
/// <summary>
/// Give a sequence of number, find the longest increasing subsequence
/// </summary>
/// <param name="numbers"></param>
/// <returns></returns>
public static string GetLongest(int[] numbers)
{
//var g = new DirectedGraph(numbers.Length);
var g = new DirectedGraph(10);
for (var i = 0; i < numbers.Length; i++)
{
for (var j = i + 1; j < numbers.Length; j++)
{
if (numbers[i] < numbers[j])
{
g.AddEdge(numbers[i], numbers[j], 1);
}
}
}
g.ReverseGraph();
Debug.WriteLine(Dfs.StrongConnectedComponentAlgorithm(g));
var v = Dfs.GetSource(g);
g.ReverseGraph();//reverse back
var stats = Dijkstra.LongestPath(g, v);
//Debug.WriteLine(stats);
return string.Empty;
}
public static DfsStats StrongConnectedComponentAlgorithm(DirectedGraph g)
{
g.ReverseGraph();//reverse G
var linearization = GetLinearization(g);
var ds = new DfsStats(g.V) { Clock = 1, ComponentCount = 0 };
g.ReverseGraph();//reverse G back
foreach (var v in linearization)
{
if (!ds.Visited[v])
{
ds.ComponentCount++;
Explore(g, v, ds);
}
}
return ds;
}
/// <summary>
/// Get predecessor of a DAG
/// </summary>
/// <param name="g">Graph g to be searched</param>
/// <returns>Predecessor of a node of a DAG</returns>
public static int GetSource(DirectedGraph g)
{
var ds = StrongConnectedComponentAlgorithm(g);
return ds.Linearization.ToArray()[0];
}
