public static int[] _2Satisfiability(DirectedGraph g)
{
MetaGraph m = new MetaGraph(g);
//return m.stack.ToArray();
//m.id.Length ~ m.stack.Count
//m.id[2 * i + 1] ~ m.stack.ElementAt()
for (int i = 0; i < m.id.Length / 2; i++)
//for (int i = 0; i < m.stack.Count / 2; i++)
{
// if not solving
if (m.id[2 * i] == m.id[2 * i + 1])
//if (m.stack.ElementAt(2 * i) == m.stack.ElementAt(2 * i + 1))
{
return new int[1] { 0 };
}
}
int[] res = new int[m.id.Length / 2 + 1];
//int[] res = new int[m.stack.Count / 2 + 1];
res[0] = 1;
// see Algorithms by Dasgupta, Papadimitriou, Vazirani. McGraw-Hill. 2006, page 102, task 3.28
for (int i = m.id.Length; i > 0; i--)
//for (int i = m.stack.Count; i > 0; i--)
{
for (int v = 0; v < m.id.Length; v++)
//for (int v = 0; v < m.stack.Count; v++)
{
if (m.id[v] != i)
//if (m.stack.ElementAt(v) != i)
{
continue;
}
if (res[v / 2 + 1] != 0)
{
continue;
}
int r;
if (v % 2 == 0)
{
r = (v + 2) / (+2);
}
else
{
r = (v + 1) / (-2);
}
res[v / 2 + 1] = r;
}
}
return res;
}
public _2Satisfiability(string file)
{
string path = Utils.GetFullPathFile(file);
try
{
using (StreamReader reader = new StreamReader(path))
{
string line;
int i = -1;
string[] param;
int CountClauses = 0;
int CountVertices;
line = reader.ReadLine();
int CountConjunctions = int.Parse(line);
g = new DirectedGraph[CountConjunctions];
while ((line = reader.ReadLine()) != null)
{
if (line == "")
{
continue;
}
if (CountClauses == 0)
{
param = line.Split(' ');
CountVertices = 2 * int.Parse(param[0]);
CountClauses = int.Parse(param[1]);
i++;
g[i] = new DirectedGraph(CountVertices);
continue;
}
param = line.Split(' ');
int v0 = Int32.Parse(param[0]);
int v1 = Int32.Parse(param[1]);
g[i].AddEdge(Index(-v0), Index(v1));
g[i].AddEdge(Index(-v1), Index(v0));
CountClauses--;
}
}
}
catch (Exception e)
{
Console.WriteLine("The file could not be read:");
Console.WriteLine(e.Message);
}
}
public DirectedGraphs(string file)
{
string path = Utils.GetFullPathFile(file);
try
{
using (StreamReader reader = new StreamReader(path))
{
string line;
int i = -1;
string[] param;
int CountEdges = 0;
int CountVertices;
line = reader.ReadLine();
int CountGraphs = int.Parse(line);
g = new DirectedGraph[CountGraphs];
while ((line = reader.ReadLine()) != null)
{
if (line == "")
{
continue;
}
if (CountEdges == 0)
{
param = line.Split(' ');
CountVertices = int.Parse(param[0]);
CountEdges = int.Parse(param[1]);
i++;
g[i] = new DirectedGraph(CountVertices);
continue;
}
param = line.Split(' ');
int from = Int32.Parse(param[0]) - 1;
int to = Int32.Parse(param[1]) - 1;
g[i].AddEdge(from, to);
CountEdges--;
}
}
}
catch (Exception e)
{
Console.WriteLine("The file could not be read:");
Console.WriteLine(e.Message);
}
}
internal static DirectedGraph CreateReverseGraph(DirectedGraph g)
{
var countVerices = g.g.Length;
DirectedGraph ng = new DirectedGraph(countVerices);
for (int v = 0; v < countVerices; v++)
{
foreach (int n in g.g[v])
{
ng.AddEdge(n, v);
}
}
return ng;
}
public MetaGraph(DirectedGraph g)
{
// do dfs on graph
this.g = g;
int l = this.g.g.Length;
marked = new bool[l];
id = new int[l];
for (int v = 0; v < g.g.Length; v++)
{
if (marked[v])
{
continue;
}
Dfs(v);
}
// do dfs on reverse (transposed) graph
this.g = Algorithms.CreateReverseGraph(this.g);
for (int i = 0; i < marked.Length; i++)
{
marked[i] = false;
}
//while(stack.Count != 0)
foreach(int v in stack)
{
//int v = stack.Pop();
if (marked[v])
{
continue;
}
DfsReverse(v);
count++;
}
this.g = g;
}
public Dfs(DirectedGraph g, int v)
{
marked = new bool[g.g.Length];
dfs(g, v);
}
private void dfs(DirectedGraph g, int v)
{
if (marked[v])
{
return;
}
marked[v] = true;
foreach (int w in g.g[v])
{
dfs(g, w);
}
}
public Dfs(DirectedGraph g, int v)
{
marked = new bool[g.g.Length];
dfs(g, v);
}
public FloydWarshal(DirectedGraph g)
{
int countVertices = g.g.Length;
dist = new int[countVertices, countVertices];
for (int i = 0; i < countVertices; i++)
{
for (int j = 0; j < countVertices; j++)
{
dist[i, j] = Int32.MaxValue / 4;
}
}
for (int i = 0; i < countVertices; i++)
{
dist[i, i] = 0;
}
for (int i = 0; i < countVertices; i++)
{
foreach (int v in g.g[i])
{
dist[i, v] = 1;
}
}
for (int k = 0; k < countVertices; k++)
{
for (int i = 0; i < countVertices; i++)
{
for (int j = 0; j < countVertices; j++)
{
dist[i, j] = Math.Min(dist[i, j], dist[i, k] + dist[k, j]);
//if (dist[i,j] > dist[i,k] + dist[k,j])
//{
// dist[i,j] = dist[i,k] + dist[k,j];
//}
}
}
}
}
public static int SemiConnected1(DirectedGraph g)
{
// http://himangi774.blogspot.ru/2013/12/check-if-graph-is-strongl-connected.html
Algorithms.SCC scc = new Algorithms.SCC(g);
//foreach (var v in scc.stack)
//{
// Console.Write(v + " ");
//}
//Console.WriteLine();
//while (scc.stack.Count != 0)
//{
// Console.Write(scc.stack.Pop() + " ");
//}
//Console.WriteLine();
var prev = scc.stack.Pop();
while (scc.stack.Count != 0)
{
var curr = scc.stack.Pop();
if (curr != prev - 1)
{
return -1;
}
prev = curr;
}
return 1;
}
public static int SemiConnected0(DirectedGraph g)
{
Algorithms.FloydWarshal fw = new Algorithms.FloydWarshal(g);
int il = fw.dist.GetLength(0);
int jl = fw.dist.GetLength(1);
//for (int i = 0; i < il; i++)
//{
// for (int j = 0; j < jl; j++)
// {
// Console.Write(fw.dist[i, j] + " ");
// }
// Console.WriteLine();
//}
//Console.WriteLine();
bool res;
for (int i = 0; i < il; i++)
{
res = true;
for (int j = 0; j < jl; j++)
{
if (fw.dist[i,j] == Int32.MaxValue / 4)
{
res = false;
break;
}
}
if (res)
{
return 1;
}
}
return -1;
}
public static int ReachableFrom(DirectedGraph g)
{
for (int i = 0; i < g.g.Length; i++)
{
Algorithms.Dfs dfs = new Algorithms.Dfs(g, i);
//if (dfs.GetResult())
//{
// return i + 1;
//}
bool res = true;
for (int j = 0; j < dfs.marked.Length; j++)
{
if (dfs.marked[j] == false)
{
res = false;
break;
}
}
if (res)
{
return i + 1;
}
}
return -1;
}