public static void FordFulkerson(DrawingSurface ds)
{
if (ds.IsUndirected())
{
var err = new ErrorBox("Graph have to be directed!");
err.ShowDialog();
return;
}
if (ds.ContainsNegativeEdge())
{
var err = new ErrorBox("Graph can not contain negative edges!");
err.ShowDialog();
return;
}
Dictionary <int, List <Edge> > adjList = ds.GetDestAdjList();
(var source, var sink) = GetSourceAndSink(adjList);
if (source == -1 || sink == -1)
{
var err = new ErrorBox("Graph have to contain source and sink!");
err.ShowDialog();
return;
}
;
var fulkersonItems = new FulkersonItem[adjList.Count, adjList.Count];
var minimalFlow = .0;
var flows = new List <double>();
msg.MoveToCorner(ds.FindForm() as Form1);
msg.SetTitle("Ford-Fulkerson algorithm result:\n");
msg.StartMenu();
for (var i = 0; i < adjList.Count; ++i)
{
for (var j = 0; j < adjList.Count; ++j)
{
fulkersonItems[i, j] = new FulkersonItem();
}
}
for (var start = 0; start < adjList.Count; ++start)
{
foreach (var edge in adjList[start])
{
fulkersonItems[start, edge.end].toFlow = edge.w;
edge.SetLabel($"{edge.w}/{0}");
}
}
while (minimalFlow != -1)
{
ds.Vertices[source].fillColor = Color.Green;
ds.Vertices[sink].fillColor = Color.Red;
ds.Invalidate();
minimalFlow = ProcessFulkerson(source, sink, adjList, ref fulkersonItems, ds);
if (minimalFlow != -1)
{
flows.Add(minimalFlow);
}
ClearVertices(ds);
ClearEdges(ds, false);
}
AlgorithmDone(ds);
msg.AddText($"Total maximal flow:\n");
msg.AddText("f(G) = ");
for (var i = 0; i < flows.Count; ++i)
{
msg.AddText($"{flows[i]} ");
if (i != flows.Count - 1)
{
msg.AddText("+ ");
}
Thread.Sleep(700);
}
msg.AddText($"= {flows.Sum()}");
msg.WaitOne();
ClearVertices(ds);
ClearEdges(ds, true);
}
public static void PrimSpanningTree(DrawingSurface ds)
{
if (!ds.IsFullyConnected() || ds.IsDirected())
{
ErrorBox err = new ErrorBox("Graph has to be undirected and fully connected");
err.ShowDialog();
return;
}
const int INF = int.MaxValue;
var vertexNum = ds.Vertices.Count;
var spanningTreeColor = Color.Red;
var adjMatrix = ds.GetDistMatrix();
var used = new bool[vertexNum];
double[] minEdge = Enumerable.Repeat((double)INF, vertexNum).ToArray();
int[] selectedEdge = Enumerable.Repeat(-1, vertexNum).ToArray();
minEdge[0] = 0;
for (var i = 0; i < vertexNum; ++i)
{
var vertex = -1;
for (var j = 0; j < vertexNum; ++j)
{
if (!used[j] && (vertex == -1 || minEdge[j] < minEdge[vertex]))
{
vertex = j;
}
}
if (minEdge[vertex] == INF)
{
ErrorBox err = new ErrorBox("Minimum spanning tree cannot be found");
err.ShowDialog();
return;
}
used[vertex] = true;
if (selectedEdge[vertex] != -1)
{
for (var k = 0; k < ds.Edges.Count; ++k)
{
if (((ds.Edges[k].start == vertex && ds.Edges[k].end == selectedEdge[vertex]) ||
(ds.Edges[k].start == selectedEdge[vertex] && ds.Edges[k].end == vertex)))
{
ds.Edges[k].fillColor = spanningTreeColor;
ds.Invalidate();
ds.Vertices[ds.Edges[k].start].fillColor = spanningTreeColor;
ds.Vertices[ds.Edges[k].end].fillColor = spanningTreeColor;
ds.Invalidate();
Thread.Sleep(2000);
}
}
}
for (var toVertex = 0; toVertex < vertexNum; ++toVertex)
{
if (adjMatrix[vertex, toVertex] < minEdge[toVertex])
{
minEdge[toVertex] = adjMatrix[vertex, toVertex];
selectedEdge[toVertex] = vertex;
}
}
}
Thread.Sleep(5000);
ClearEdges(ds);
ClearVertices(ds);
ds.Invalidate();
}
public static void Dijkstra(DrawingSurface ds, int start)
{
if (ds.ContainsNegativeEdge())
{
var err = new ErrorBox("Graph contains negative edges");
err.ShowDialog();
return;
}
Dictionary <int, List <Edge> > adjList = ds.GetDestAdjList();
var que = new C5.IntervalHeap <Edge>(new EdgeCompare());
double[] dist = Enumerable.Repeat((double)int.MaxValue, adjList.Count).ToArray();
int[] parent = Enumerable.Repeat(-1, adjList.Count).ToArray();
var visitedColor = Color.Green;
var processedColor = Color.Yellow;
var currentEdgeColor = Color.Red;
que.Add(new Edge(ds.Vertices[start], ds.Vertices[start], 0, true));
dist[start] = 0;
for (var i = 0; i < ds.Vertices.Count; ++i)
{
ds.Vertices[i].label = "INF";
}
ds.Vertices[start].label = "0";
while (que.Count != 0)
{
var currEdge = que.FindMin(); que.DeleteMin();
var startVertex = (ds.Vertices[currEdge.end].fillColor == visitedColor) ? currEdge.start : currEdge.end;
ReDrawCircle(ds, startVertex, visitedColor);
foreach (var edge in adjList[startVertex])
{
var currVertex = (edge.end != startVertex) ? edge.end : edge.start;
ReDrawEdge(ds, edge, currentEdgeColor, 300);
if (ds.Vertices[currVertex].fillColor != visitedColor)
{
ReDrawCircle(ds, currVertex, processedColor, 0);
}
Thread.Sleep(1000);
if (dist[currVertex] > dist[startVertex] + edge.w)
{
dist[currVertex] = dist[startVertex] + edge.w;
parent[currVertex] = startVertex;
ds.Vertices[currVertex].label = $"{Math.Round(dist[currEdge.end], 3)}+{Math.Round(edge.w, 3)}";
ds.Invalidate();
Thread.Sleep(1000);
que.Add(edge);
}
ds.Vertices[currVertex].label = (dist[currVertex] == int.MaxValue) ? "INF" : $"{dist[currVertex]}";
ReDrawEdge(ds, edge, Color.Gray, 0);
}
}
msg.SetTitle("Dijkstra algorithm result:");
msg.MoveToCorner(ds.FindForm() as Form1);
msg.StartMenu();
for (var target = 0; target < adjList.Count; ++target)
{
if (start != target)
{
var currWay = GetWay(start, target, parent);
PrintWay(currWay, dist[target]);
Thread.Sleep(1000);
}
}
msg.WaitOne();
ClearEdges(ds);
ClearVertices(ds);
}
public static void BackTrackingColouring(DrawingSurface ds, int colorAmount)
{
bool isSafe(int[,] adjmat, int[] color)
{
for (var i = 0; i < ds.Vertices.Count; ++i)
{
for (var j = i + 1; j < ds.Vertices.Count; ++j)
{
if (adjmat[i, j] == 1 && color[j] == color[i])
{
return(false);
}
}
}
return(true);
}
bool GraphColouring(int[,] adjmat, int bound, int index, int[] color)
{
if (index == ds.Vertices.Count)
{
if (isSafe(adjmat, color))
{
for (var k = 0; k < ds.Vertices.Count; ++k)
{
ReDrawCircle(ds, k, colors[color[k]]);
}
return(true);
}
return(false);
}
for (var j = 1; j <= bound; ++j)
{
color[index] = j;
if (GraphColouring(adjmat, bound, index + 1, color))
{
return(true);
}
color[index] = 0;
}
return(false);
}
var adjMatrix = ds.GetAdjMatrix();
var colorsList = new List <int> {
};
if (!ds.IsUndirected())
{
var err = new ErrorBox("Graph has to be unoriented");
err.ShowDialog();
return;
}
for (var i = 0; i < ds.Vertices.Count; ++i)
{
colorsList.Add(0);
}
if (!GraphColouring(adjMatrix, colorAmount, 0, colorsList.ToArray()))
{
var err = new ErrorBox($"Graph cannot be coloured into {colorAmount} colours");
err.ShowDialog();
return;
}
Thread.Sleep(5000);
ClearVertices(ds);
}
