// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2015 Google Inc. All rights reserved.
// http://ceres-solver.org/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution.
// * Neither the name of Google Inc. nor the names of its contributors may be
//   used to endorse or promote products derived from this software without
//   specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// Author: sameeragarwal@google.com (Sameer Agarwal)

#ifndef CERES_INTERNAL_SINGLE_LINKAGE_CLUSTERING_H_
#define CERES_INTERNAL_SINGLE_LINKAGE_CLUSTERING_H_

#include <unordered_map>

#include "ceres/graph.h"
#include "ceres/internal/port.h"

namespace ceres {
namespace internal {

struct SingleLinkageClusteringOptions {
  // Graph edges with edge weight less than min_similarity are ignored
  // during the clustering process.
  double min_similarity = 0.99;
};

// Compute a partitioning of the vertices of the graph using the
// single linkage clustering algorithm. Edges with weight less than
// SingleLinkageClusteringOptions::min_similarity will be ignored.
//
// membership upon return will contain a mapping from the vertices of
// the graph to an integer indicating the identity of the cluster that
// it belongs to.
//
// The return value of this function is the number of clusters
// identified by the algorithm.
int CERES_EXPORT_INTERNAL
ComputeSingleLinkageClustering(const SingleLinkageClusteringOptions& options,
                               const WeightedGraph<int>& graph,
                               std::unordered_map<int, int>* membership);

}  // namespace internal
}  // namespace ceres

#endif  // CERES_INTERNAL_SINGLE_LINKAGE_CLUSTERING_H_