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diff --git a/elki/src/main/java/de/lmu/ifi/dbs/elki/algorithm/clustering/ClusteringAlgorithmUtil.java b/elki/src/main/java/de/lmu/ifi/dbs/elki/algorithm/clustering/ClusteringAlgorithmUtil.java
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+++ b/elki/src/main/java/de/lmu/ifi/dbs/elki/algorithm/clustering/ClusteringAlgorithmUtil.java
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+package de.lmu.ifi.dbs.elki.algorithm.clustering;
+
+/*
+ This file is part of ELKI:
+ Environment for Developing KDD-Applications Supported by Index-Structures
+
+ Copyright (C) 2015
+ Ludwig-Maximilians-Universität München
+ Lehr- und Forschungseinheit für Datenbanksysteme
+ ELKI Development Team
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Affero General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU Affero General Public License for more details.
+
+ You should have received a copy of the GNU Affero General Public License
+ along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+import de.lmu.ifi.dbs.elki.database.datastore.IntegerDataStore;
+import de.lmu.ifi.dbs.elki.database.ids.ArrayModifiableDBIDs;
+import de.lmu.ifi.dbs.elki.database.ids.DBIDIter;
+import de.lmu.ifi.dbs.elki.database.ids.DBIDUtil;
+import de.lmu.ifi.dbs.elki.database.ids.DBIDs;
+
+/**
+ * Utility functionality for writing clustering algorithms.
+ *
+ * @author Erich Schubert
+ */
+public class ClusteringAlgorithmUtil {
+  /**
+   * Collect clusters from their [0;k-1] integer labels.
+   * 
+   * @param ids Objects
+   * @param assignment Cluster assignment
+   * @param k Number of labels (must be labeled 0 to k-1)
+   * @return Partitions
+   */
+  public static ArrayModifiableDBIDs[] partitionsFromIntegerLabels(DBIDs ids, IntegerDataStore assignment, int k) {
+    int[] sizes = new int[k];
+    for(DBIDIter iter = ids.iter(); iter.valid(); iter.advance()) {
+      sizes[assignment.intValue(iter)] += 1;
+    }
+    ArrayModifiableDBIDs[] clusters = new ArrayModifiableDBIDs[k];
+    for(int i = 0; i < k; i++) {
+      clusters[i] = DBIDUtil.newArray(sizes[i]);
+    }
+    for(DBIDIter iter = ids.iter(); iter.valid(); iter.advance()) {
+      clusters[assignment.intValue(iter)].add(iter);
+    }
+    return clusters;
+  }
+}