internal Edge FindEdgeTo(Vertex v)
{
foreach(Edge e in forward)
if(e.to == v)
return e;
return null;
}
public Edge(Vertex from, Vertex to, int capacity, int flow, object extraInfo)
{
this.from = from;
this.to = to;
this.capacity = capacity;
this.flow = flow;
this.extraInfo = extraInfo;
}
/// <summary>
/// Finds all property value reachable with solid edges only
/// </summary>
/// <param name="v"></param>
protected void FindGoodValues(Vertex v)
{
foreach(Edge e in v.forward)
if (e.capacity > 1)
if (visited[e.to.ID] == 0)
{
visited[e.to.ID] = 1;
whiteVerticesCount++;
if (e.to.PropertyValue != -1)
goodEndValues.Add(e.to.PropertyValue);
FindGoodValues(e.to);
}
}
public int FordFulkerson()
{
int flow = 0;
// TODO: don't need to allocate so many, gauze the buffer size carefully to reduce its size
int dmax = vertices.Count;
int mincutValue;
Vertex[] d = new Vertex[dmax];
int d1, d2;
IEnumerator<Vertex> iter;
ArrayList aMinCut = new ArrayList();
Vertex p;
Edge tmpe;
while(true)
{
iter = vertices.GetEnumerator();
while(iter.MoveNext())
iter.Current.back = null;
source.back = source;
d[0] = source;
d1 = 0;
d2 = 1;
while(d1 != d2)
{
foreach(Edge e in d[d1].forward)
if(e.flow < e.capacity)
if(e.to.back == null)
{
e.to.back = d[d1];
e.to.backType = 1;
d[d2] = e.to;
d2 = (d2 + 1) % dmax;
if(d2 == d1)
{
Console.WriteLine("FATAL ERROR: Buffer is not long enough");
}
}
foreach(Edge e in d[d1].backward)
if(e.flow > 0)
if(e.from.back == null)
{
e.from.back = d[d1];
e.from.backType = 2;
d[d2] = e.from;
d2 = (d2 + 1) % dmax;
if(d2 == d1)
{
Console.WriteLine("FATAL ERROR: Buffer is not long enough");
}
}
d1++;
// found a path, can stop now
if(sink.back != null)
break;
}
// done searching for path, now check whether we can increase the flow
if(sink.back == null)
break;
flow++;
p = sink;
while(p != source)
{
if(p.backType == 1)
{
tmpe = p.back.FindEdgeTo(p);
tmpe.flow++;
}
else
{
tmpe = p.FindEdgeTo(p.back);
tmpe.flow--;
}
p = p.back;
}
}
// now we can use the information stored in .back to find the mincut
iter = vertices.GetEnumerator();
mincutValue = 0;
while(iter.MoveNext())
{
Vertex v = iter.Current;
if(v.back != null)
foreach(Edge e in v.forward)
if(e.to.back == null)
{
aMinCut.Add(e);
mincutValue += e.flow;
}
}
mincut = new Edge[aMinCut.Count];
for(int i = 0; i < mincut.Length; i++)
mincut[i] = (Edge)aMinCut[i];
// correctness check of output
if(mincutValue != flow)
Console.WriteLine("Mincut != flow");
iter = vertices.GetEnumerator();
int sum;
while(iter.MoveNext())
{
p = iter.Current;
sum = 0;
foreach(Edge e in p.forward)
{
if(e.capacity < e.flow)
Console.WriteLine("flow > capacity");
sum += e.flow;
}
foreach(Edge e in p.backward)
sum -= e.flow;
if(p == source)
{
if(sum != flow)
Console.WriteLine("flow from source is wrong");
}
else if(p == sink)
{
if(sum != -flow)
Console.WriteLine("flow to sink is wrong");
}else if(sum != 0)
Console.WriteLine("flow in != flow out");
}
return flow;
}
