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+/* This file is part of the Gudhi Library. The Gudhi library 
+ *    (Geometric Understanding in Higher Dimensions) is a generic C++ 
+ *    library for computational topology.
+ *
+ *    Author(s):       David Salinas
+ *
+ *    Copyright (C) 2014  INRIA Sophia Antipolis-Mediterranee (France)
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the GNU 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 General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * 
+ */
+
+#ifndef UTILS_K_NEAREST_BUILDER_H_
+#define UTILS_K_NEAREST_BUILDER_H_
+
+#include <CGAL/Euclidean_distance.h>
+#include <CGAL/Orthogonal_k_neighbor_search.h>
+#include <CGAL/Search_traits_d.h>
+#include <CGAL/Search_traits_adapter.h>
+#include <CGAL/property_map.h>
+
+#include <unordered_map>
+#include <list>
+#include <utility>
+
+#include "utils/UI_utils.h"
+#include "model/Complex_typedefs.h"
+
+template<typename SkBlComplex> class K_nearest_builder {
+ private:
+  typedef Geometry_trait Kernel;
+  typedef Point Point_d;
+  typedef std::pair<Point_d, unsigned> Point_d_with_id;
+  typedef CGAL::Search_traits_d<Kernel> Traits_base;
+  typedef CGAL::Search_traits_adapter<Point_d_with_id, CGAL::First_of_pair_property_map<Point_d_with_id>,
+      Traits_base> Traits;
+  typedef CGAL::Orthogonal_k_neighbor_search<Traits> Neighbor_search;
+  typedef Neighbor_search::Tree Tree;
+  typedef Neighbor_search::Distance Distance;
+
+  SkBlComplex& complex_;
+
+ public:
+  /**
+   * @brief Modify complex to be the expansion of the k-nearest neighbor
+   * symetric graph.
+   */
+  K_nearest_builder(SkBlComplex& complex, unsigned k) : complex_(complex) {
+    complex.keep_only_vertices();
+    compute_edges(k);
+  }
+
+ private:
+  double squared_eucl_distance(const Point& p1, const Point& p2) const {
+    return Geometry_trait::Squared_distance_d()(p1, p2);
+  }
+
+  void compute_edges(unsigned k) {
+    std::list<Point_d_with_id> points_with_id;
+    for (auto v : complex_.vertex_range()) {
+      Point_d_with_id point_v(complex_.point(v), v.vertex);
+      points_with_id.push_back(point_v);
+    }
+
+    Tree tree(points_with_id.begin(), points_with_id.end());
+
+    typedef typename SkBlComplex::Vertex_handle Vertex_handle;
+    for (auto p : complex_.vertex_range()) {
+      Neighbor_search search(tree, complex_.point(p), k + 1);
+      for (auto it = ++search.begin(); it != search.end(); ++it) {
+        Vertex_handle q(std::get<1>(it->first));
+        if (p != q && complex_.contains_vertex(p) && complex_.contains_vertex(q))
+          complex_.add_edge(p, q);
+      }
+    }
+  }
+};
+
+#endif  // UTILS_K_NEAREST_BUILDER_H_