/// <summary>
/// Solves the 2-SAT problem and returns a possible variable assignment if it exits.
/// </summary>
/// <returns>The variable assignment, or null if no solution exists.</returns>
public bool[] Solve()
{
var sc = new StrongComponents(graph);
scGraph = sc.CreateGraph();
literalValue = new bool[n * 2];
for (int i = 0; i < n; i++)
{
if (graph.vcomp[i * 2] == graph.vcomp[i * 2 + 1])
{
return(null);
}
}
literalMap = new List <int> [scGraph.Length];
for (int i = 0; i < scGraph.Length; i++)
{
literalMap[i] = new List <int>();
}
for (int i = 0; i < n * 2; i++)
{
literalMap[graph.vcomp[i]].Add(i);
}
visited = new bool[scGraph.Length];
conflict = new bool[scGraph.Length];
for (int i = 0; i < scGraph.Length; i++)
{
Dfs(i);
}
var var = new bool[n];
for (int i = 0; i < n; i++)
{
if (!literalValue[i * 2] && !literalValue[i * 2 + 1])
{
return(null);
}
var[i] = literalValue[i * 2];
}
return(var);
}
