81 lines
2.2 KiB
C++
81 lines
2.2 KiB
C++
// Copyright (c) 2000 Max-Planck-Institute Saarbruecken (Germany).
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// All rights reserved.
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//
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// This file is part of CGAL (www.cgal.org).
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//
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// $URL: https://github.com/CGAL/cgal/blob/v5.1/Partition_2/include/CGAL/is_y_monotone_2.h $
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// $Id: is_y_monotone_2.h 0779373 2020-03-26T13:31:46+01:00 Sébastien Loriot
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// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
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//
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//
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// Author(s) : Susan Hert <hert@mpi-sb.mpg.de>
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#ifndef CGAL_IS_Y_MONOTONE_2_H
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#define CGAL_IS_Y_MONOTONE_2_H
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#include <CGAL/license/Partition_2.h>
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#include <CGAL/circulator.h>
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#include <CGAL/ch_selected_extreme_points_2.h>
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#include <iterator>
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#include <list>
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namespace CGAL {
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template<class InputIterator, class Traits>
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bool
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is_y_monotone_2(InputIterator first, InputIterator last,
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const Traits& traits)
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{
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typedef typename Traits::Point_2 Point_2;
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typedef typename Traits::Less_yx_2 Less_yx_2;
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typedef std::list<Point_2> Vertex_list;
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typedef typename Vertex_list::iterator I;
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typedef Circulator_from_iterator<I> Circulator;
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Vertex_list polygon(first, last);
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I n_point_ref;
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I s_point_ref;
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// find the extreme north and south points
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ch_n_point(polygon.begin(), polygon.end(), n_point_ref, traits);
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ch_s_point(polygon.begin(), polygon.end(), s_point_ref, traits);
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Circulator north_c(polygon.begin(), polygon.end(), n_point_ref);
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Circulator south_c(polygon.begin(), polygon.end(), s_point_ref);
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Less_yx_2 less_yx = traits.less_yx_2_object();
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Circulator prev_c = south_c;
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Circulator c = south_c;
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for (c++; c != north_c; c++)
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{
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if (!less_yx(*prev_c, *c)) return false;
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prev_c = c;
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}
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prev_c = north_c;
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c = north_c;
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for (c++; c != south_c; c++)
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{
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if (!less_yx(*c, *prev_c)) return false;
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prev_c = c;
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}
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return true;
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}
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template<class InputIterator>
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bool
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is_y_monotone_2(InputIterator first, InputIterator last)
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{
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typedef typename std::iterator_traits<InputIterator>::value_type Point_2;
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typedef typename Kernel_traits<Point_2>::Kernel K;
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return is_y_monotone_2(first, last, K());
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}
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}
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#endif // CGAL_IS_Y_MONOTONE_2_H
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