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+/*
+ * Is_manifold.h
+ *  Created on: Jan 28, 2015
+ * 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_IS_MANIFOLD_H_
+#define UTILS_IS_MANIFOLD_H_
+
+#include "utils/UI_utils.h"
+#include "utils/Edge_contractor.h"
+
+/**
+ * Iteratively tries to anticollapse smallest edge non added so far.
+ * If its link is contractible then no topological change and else possible topological change.
+ *
+ * todo do a sparsification with some parameter eps while growing
+ */
+template<typename SkBlComplex> class Is_manifold {
+ private:
+  const SkBlComplex& input_complex_;
+  typedef typename SkBlComplex::Vertex_handle Vertex_handle;
+
+ public:
+  /*
+   * return dim the maximum dimension around one simplex and res which is true if the complex is a manifold.
+   * If the complex has dimension <= 3 then if res is false, the complex is not a manifold.
+   * For d-manifold with d>=4, res may be false while the complex is a manifold.
+   */
+  Is_manifold(const SkBlComplex& input_complex, unsigned& dim, bool & res) : input_complex_(input_complex) {
+    res = true;
+    dim = -1;
+    if (!input_complex_.empty()) {
+      for (auto v : input_complex_.vertex_range()) {
+        dim = local_dimension(v);
+        break;
+      }
+      // check that the link of every vertex is a dim-1 sphere
+      for (auto v : input_complex_.vertex_range()) {
+        if (!is_k_sphere(v, dim - 1)) {
+          res = false;
+          break;
+        }
+      }
+    }
+  }
+
+ private:
+  unsigned local_dimension(Vertex_handle v) {
+    unsigned dim = 0;
+    for (const auto& s : input_complex_.star_simplex_range(v))
+      dim = (std::max)(dim, (unsigned) s.dimension());
+    return dim;
+  }
+
+  bool is_k_sphere(Vertex_handle v, int k) {
+    auto link = input_complex_.link(v);
+    Edge_contractor<Complex> contractor(link, link.num_vertices() - 1);
+    return (is_sphere_simplex(link) == k);
+  }
+
+  // A minimal sphere is a complex that contains vertices v1...vn and all faces
+  // made upon this set except the face {v1,...,vn}
+  // return -2 if not a minimal sphere
+  // and d otherwise if complex is a d minimal sphere
+
+  template<typename SubComplex>
+  int is_sphere_simplex(const SubComplex& complex) {
+    if (complex.empty()) return -1;
+    if (complex.num_blockers() != 1) return -2;
+
+    // necessary and sufficient condition : there exists a unique blocker that passes through all vertices
+    auto first_blocker = *(complex.const_blocker_range().begin());
+
+    if (first_blocker->dimension() + 1 != complex.num_vertices())
+      return -2;
+    else
+      return (first_blocker->dimension() - 1);
+  }
+};
+
+#endif  // UTILS_IS_MANIFOLD_H_