/// <summary>
/// Backtrack through a variable's value sets until one is found that is arc consistent.
/// </summary>
/// <param name="currentVariableIndex">Current variable index.</param>
/// <param name="snapshotAssignment">Current snapshot of value sets.</param>
/// <param name="constraintNetwork">Constraint network.</param>
/// <returns>True if a value is found to be consistent, False if a value is not found.</returns>
private bool Backtrack(int currentVariableIndex, SnapshotLabelAssignment snapshotAssignment, ConstraintNetwork constraintNetwork)
{
// Label assignment has been successful...
if (snapshotAssignment.IsComplete() && AllVariablesTested(currentVariableIndex))
{
return(true);
}
// The unassigned variable may be a regular variable or an encapsulated variable
var currentVariable = SelectUnassignedVariable(currentVariableIndex, constraintNetwork, snapshotAssignment);
foreach (var value in OrderDomainValues(currentVariable, snapshotAssignment, constraintNetwork))
{
if (IsConsistent(value, snapshotAssignment))
{
snapshotAssignment.AssignTo(value);
// Is this the final variable?
if (AllVariablesTested(currentVariableIndex))
{
return(true);
}
if (Backtrack(currentVariableIndex + 1, snapshotAssignment, constraintNetwork))
{
return(true);
}
}
snapshotAssignment.Remove(value);
}
return(false);
}
