code: private int[] reIndexIndices(SortableVertex[] sortVertices, int[] indices) {
          // Create temporary lookup-array, O(n)
          int[] indexLUT = new int[sortVertices.length];
          int[] newIndices = new int[indices.length];
  
          for (int i = 0; i < sortVertices.length; ++i) {
              indexLUT[sortVertices[i].originalIndex] = i;
          }
  
          // Convert old indices to new indices, O(n)
          for (int i = 0; i < indices.length; ++i) {
              newIndices[i] = indexLUT[indices[i]];
          }
  
  
          return newIndices;
      }
docs: Re-index all indices, based on the sorted vertices.
  
  @param sortVertices sorted vertices
  @param indices original indices
  @return reordered indices