[vtkusers] "reverse lookup" in vtkDataArray

[David Doria]

I currently have the "forward mapping" from "new id" to "old id":

vtkIdTypeArray* originalIds =
vtkIdTypeArray::SafeDownCast(selected->GetPointData()->GetArray("vtkOriginalPointIds"));

  for(vtkIdType i = 0; i < originalIds->GetNumberOfTuples(); i++)
    {
    std::cout << "Point " << i << " was originally point " <<
originalIds->GetValue(i) << std::endl;
    }

If I want the reverse mapping, i.e. "Which new id corresponds to original id
X?", is there a better way to do it than a linear search through the array?

  for(vtkIdType i = 0; i < originalIds->GetNumberOfTuples(); i++)
    {
    if(originalIds->GetValue(i) == X)
      {
      cout << "current ID corresponding to original ID X is " << i << endl;
      }
    }

This seems horribly inefficient!

Thanks,

David
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