mirror of https://github.com/CGAL/cgal
137 lines
3.8 KiB
C
137 lines
3.8 KiB
C
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// Copyright (c) 1999 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); you may redistribute it under
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// the terms of the Q Public License version 1.0.
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// See the file LICENSE.QPL distributed with CGAL.
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//
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// Licensees holding a valid commercial license may use this file in
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// accordance with the commercial license agreement provided with the software.
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//
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// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
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// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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//
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// $URL$
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// $Id$
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//
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//
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// Author(s) : Stefan Schirra
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#ifndef CGAL_CH_MELKMAN_C
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#define CGAL_CH_MELKMAN_C
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#ifndef CGAL_CH_MELKMAN_H
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#include <CGAL/ch_melkman.h>
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#endif
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#ifndef CGAL_CH_NO_POSTCONDITIONS
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#include <CGAL/convexity_check_2.h>
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#endif // CGAL_CH_NO_POSTCONDITIONS
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#include <CGAL/ch_assertions.h>
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#include <queue>
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#include <iterator>
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CGAL_BEGIN_NAMESPACE
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template <class InputIterator, class OutputIterator, class Traits>
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OutputIterator
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ch_melkman( InputIterator first, InputIterator last,
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OutputIterator result, const Traits& ch_traits)
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{
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typedef typename Traits::Point_2 Point;
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typedef typename Traits::Segment_2 Segment;
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typedef typename Traits::Equal_2 Equal_2;
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typename Traits::Left_turn_2 left_turn = ch_traits.left_turn_2_object();
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Equal_2 equal_points = ch_traits.equal_2_object();
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CGAL_ch_assertion_code( \
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typename Traits::Less_xy_2 less = ch_traits.less_xy_2_object(); )
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std::deque< Point> Q;
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CGAL_ch_expensive_postcondition_code( std::deque< Point> IN; )
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if (first == last) return result; // 0 elements
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Point p = *first;
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CGAL_ch_expensive_postcondition_code( IN.push_back(p); )
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if (++first == last)
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{ *result = p; ++result; return result; } // 1 element
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Point q = *first;
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CGAL_ch_expensive_postcondition_code( IN.push_back(q); )
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if (++first == last) // 2 elements
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{
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*result = p; ++result;
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if (! equal_points(p,q))
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{ *result = q; ++result; }
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return result;
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}
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Q.push_back( p);
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Point r;
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while (first != last)
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{
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r = *first;
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CGAL_ch_expensive_postcondition_code( IN.push_back(r); )
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// visited input sequence = p,..., q, r
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if ( left_turn(p,q,r)) { Q.push_back( q); break; }
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if ( left_turn(q,p,r)) { Q.push_front( q); break; }
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CGAL_ch_assertion( less( p, q) ? less (p, r) : less( r, p));
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q = r;
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++first;
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}
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Point current = q;
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if (first != last) // non-collinear point r exists
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{
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current = r;
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// current, Q.front(), ..., Q.back()
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// ccw convex hull of visited points
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Point s;
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while ( ++first != last)
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{
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r = *first;
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CGAL_ch_expensive_postcondition_code( IN.push_back(r); )
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if (left_turn( current, r, Q.front()) ||
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left_turn( Q.back(), r, current))
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// r outside cone Q.front(), current, Q.back() <=>
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// right_turn( current, Q.front(), r) ||
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// right_turn( Q.back(), current, r)
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{
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s = current;
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while (!Q.empty() && !left_turn( r, s, Q.front()))
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// !left_turn( r, s, Q.front())
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{ s = Q.front(); Q.pop_front(); }
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Q.push_front(s);
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s = current;
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while (!Q.empty() && !left_turn( s, r, Q.back()))
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// !right_turn( r, s, Q.back())
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{ s = Q.back(); Q.pop_back(); }
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Q.push_back(s);
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current = r;
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}
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}
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}
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Q.push_back( current); // add last point to Q
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CGAL_ch_postcondition( \
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is_ccw_strongly_convex_2( Q.begin(), Q.end(), ch_traits));
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CGAL_ch_expensive_postcondition( \
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ch_brute_force_check_2( IN.begin(),IN.end(), Q.begin(),Q.end(), ch_traits));
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std::copy( Q.begin(), Q.end(), result);
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return result;
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}
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CGAL_END_NAMESPACE
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#endif // CGAL_CH_MELKMAN_C
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