code: package ru.ifmo.nds.ndt;
  
  import ru.ifmo.nds.NonDominatedSorting;
  import ru.ifmo.nds.util.ArrayHelper;
  import ru.ifmo.nds.util.ArraySorter;
  
  public class ENS_NDT_OneTree extends NonDominatedSorting {
      private SplitBuilder splitBuilder;
      private int[] ranks;
      private double[][] transposedPoints;
      private double[][] points;
      private final int threshold;
  
      public ENS_NDT_OneTree(int maximumPoints, int maximumDimension, int threshold) {
          super(maximumPoints, maximumDimension);
          this.threshold = threshold;
          ranks = new int[maximumPoints];
          transposedPoints = new double[maximumDimension][];
          for (int d = 1; d < maximumDimension; ++d) {
              transposedPoints[d] = new double[maximumPoints];
          }
          splitBuilder = new SplitBuilder(transposedPoints, maximumPoints, threshold);
          points = new double[maximumPoints][];
      }
  
      @Override
      public String getName() {
          return "ENS-NDT OneTree (Objects, threshold = " + threshold + ")";
      }
  
      @Override
      protected void closeImpl() {
          splitBuilder = null;
          ranks = null;
          transposedPoints = null;
          points = null;
      }
  
      @Override
      protected void sortChecked(double[][] points, int[] ranks, int maximalMeaningfulRank) {
          int n = points.length;
          int dim = points[0].length;
          ArrayHelper.fillIdentity(indices, n);
          sorter.lexicographicalSort(points, indices, 0, n, dim);
  
          int newN = ArraySorter.retainUniquePoints(points, indices, this.points, ranks);
          this.ranks[0] = 0;
  
          TreeRankNode tree = threshold == 1 ? TreeRankNode.EMPTY_1 : TreeRankNode.EMPTY;
          for (int i = 0; i < newN; ++i) {
              for (int j = 1; j < dim; ++j) {
                  transposedPoints[j][i] = this.points[i][j];
              }
          }
  
          Split split = splitBuilder.result(newN, dim);
  
          tree = tree.add(this.points[0], 0, split, threshold);
          int maxObj = dim - 1;
          for (int i = 1; i < newN; ++i) {
              double[] current = this.points[i];
              int currRank = tree.evaluateRank(current, 0, split, maxObj);
              this.ranks[i] = currRank;
              if (currRank <= maximalMeaningfulRank) {
                  tree = tree.add(current, currRank, split, threshold);
              }
          }
  
          for (int i = 0; i < n; ++i) {
              ranks[i] = this.ranks[ranks[i]];
              this.points[i] = null;
          }
      }
  }
  