diff --git a/lemon/matching.h b/lemon/matching.h
--- a/lemon/matching.h
+++ b/lemon/matching.h
@@ -810,41 +810,60 @@
       if (!_matching) {
         _matching = new MatchingMap(_graph);
       }
+
       if (!_node_potential) {
         _node_potential = new NodePotential(_graph);
       }
+
       if (!_blossom_set) {
         _blossom_index = new IntNodeMap(_graph);
         _blossom_set = new BlossomSet(*_blossom_index);
         _blossom_data = new RangeMap<BlossomData>(_blossom_num);
+      } else if (_blossom_data->size() != _blossom_num) {
+        delete _blossom_data;
+        _blossom_data = new RangeMap<BlossomData>(_blossom_num);
       }
 
       if (!_node_index) {
         _node_index = new IntNodeMap(_graph);
         _node_heap_index = new IntArcMap(_graph);
         _node_data = new RangeMap<NodeData>(_node_num,
-                                              NodeData(*_node_heap_index));
+                                            NodeData(*_node_heap_index));
+      } else {
+        delete _node_data;
+        _node_data = new RangeMap<NodeData>(_node_num,
+                                            NodeData(*_node_heap_index));
       }
 
       if (!_tree_set) {
         _tree_set_index = new IntIntMap(_blossom_num);
         _tree_set = new TreeSet(*_tree_set_index);
+      } else {
+        _tree_set_index->resize(_blossom_num);
       }
+
       if (!_delta1) {
         _delta1_index = new IntNodeMap(_graph);
         _delta1 = new BinHeap<Value, IntNodeMap>(*_delta1_index);
       }
+
       if (!_delta2) {
         _delta2_index = new IntIntMap(_blossom_num);
         _delta2 = new BinHeap<Value, IntIntMap>(*_delta2_index);
+      } else {
+        _delta2_index->resize(_blossom_num);
       }
+
       if (!_delta3) {
         _delta3_index = new IntEdgeMap(_graph);
         _delta3 = new BinHeap<Value, IntEdgeMap>(*_delta3_index);
       }
+
       if (!_delta4) {
         _delta4_index = new IntIntMap(_blossom_num);
         _delta4 = new BinHeap<Value, IntIntMap>(*_delta4_index);
+      } else {
+        _delta4_index->resize(_blossom_num);
       }
     }
 
@@ -1588,6 +1607,9 @@
     void init() {
       createStructures();
 
+      _blossom_node_list.clear();
+      _blossom_potential.clear();
+
       for (ArcIt e(_graph); e != INVALID; ++e) {
         (*_node_heap_index)[e] = BinHeap<Value, IntArcMap>::PRE_HEAP;
       }
@@ -1601,9 +1623,16 @@
         (*_delta2_index)[i] = _delta2->PRE_HEAP;
         (*_delta4_index)[i] = _delta4->PRE_HEAP;
       }
-
+      
       _unmatched = _node_num;
 
+      _delta1->clear();
+      _delta2->clear();
+      _delta3->clear();
+      _delta4->clear();
+      _blossom_set->clear();
+      _tree_set->clear();
+
       int index = 0;
       for (NodeIt n(_graph); n != INVALID; ++n) {
         Value max = 0;
@@ -1614,6 +1643,8 @@
           }
         }
         (*_node_index)[n] = index;
+        (*_node_data)[index].heap_index.clear();
+        (*_node_data)[index].heap.clear();
         (*_node_data)[index].pot = max;
         _delta1->push(n, max);
         int blossom =
@@ -2237,13 +2268,18 @@
       if (!_matching) {
         _matching = new MatchingMap(_graph);
       }
+
       if (!_node_potential) {
         _node_potential = new NodePotential(_graph);
       }
+
       if (!_blossom_set) {
         _blossom_index = new IntNodeMap(_graph);
         _blossom_set = new BlossomSet(*_blossom_index);
         _blossom_data = new RangeMap<BlossomData>(_blossom_num);
+      } else if (_blossom_data->size() != _blossom_num) {
+        delete _blossom_data;
+        _blossom_data = new RangeMap<BlossomData>(_blossom_num);
       }
 
       if (!_node_index) {
@@ -2251,23 +2287,36 @@
         _node_heap_index = new IntArcMap(_graph);
         _node_data = new RangeMap<NodeData>(_node_num,
                                             NodeData(*_node_heap_index));
+      } else if (_node_data->size() != _node_num) {
+        delete _node_data;
+        _node_data = new RangeMap<NodeData>(_node_num,
+                                            NodeData(*_node_heap_index));
       }
 
       if (!_tree_set) {
         _tree_set_index = new IntIntMap(_blossom_num);
         _tree_set = new TreeSet(*_tree_set_index);
+      } else {
+        _tree_set_index->resize(_blossom_num);
       }
+
       if (!_delta2) {
         _delta2_index = new IntIntMap(_blossom_num);
         _delta2 = new BinHeap<Value, IntIntMap>(*_delta2_index);
+      } else {
+        _delta2_index->resize(_blossom_num);
       }
+
       if (!_delta3) {
         _delta3_index = new IntEdgeMap(_graph);
         _delta3 = new BinHeap<Value, IntEdgeMap>(*_delta3_index);
       }
+
       if (!_delta4) {
         _delta4_index = new IntIntMap(_blossom_num);
         _delta4 = new BinHeap<Value, IntIntMap>(*_delta4_index);
+      } else {
+        _delta4_index->resize(_blossom_num);
       }
     }
 
@@ -2968,6 +3017,9 @@
     void init() {
       createStructures();
 
+      _blossom_node_list.clear();
+      _blossom_potential.clear();
+
       for (ArcIt e(_graph); e != INVALID; ++e) {
         (*_node_heap_index)[e] = BinHeap<Value, IntArcMap>::PRE_HEAP;
       }
@@ -2981,6 +3033,12 @@
 
       _unmatched = _node_num;
 
+      _delta2->clear();
+      _delta3->clear();
+      _delta4->clear();
+      _blossom_set->clear();
+      _tree_set->clear();
+
       int index = 0;
       for (NodeIt n(_graph); n != INVALID; ++n) {
         Value max = - std::numeric_limits<Value>::max();
@@ -2991,6 +3049,8 @@
           }
         }
         (*_node_index)[n] = index;
+        (*_node_data)[index].heap_index.clear();
+        (*_node_data)[index].heap.clear();
         (*_node_data)[index].pot = max;
         int blossom =
           _blossom_set->insert(n, std::numeric_limits<Value>::max());
diff --git a/lemon/unionfind.h b/lemon/unionfind.h
--- a/lemon/unionfind.h
+++ b/lemon/unionfind.h
@@ -1288,6 +1288,15 @@
       : index(_index), first_class(-1),
         first_free_class(-1), first_free_node(-1) {}
 
+    /// \brief Clears the union-find data structure
+    ///
+    /// Erase each item from the data structure.
+    void clear() {
+      nodes.clear();
+      classes.clear();
+      first_free_node = first_free_class = first_class = -1;
+    }
+
     /// \brief Insert a new node into a new component.
     ///
     /// Insert a new node into a new component.