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// Copyright (c) 1999 Max-Planck-Institute Saarbruecken (Germany).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org); you may redistribute it under
// the terms of the Q Public License version 1.0.
// See the file LICENSE.QPL distributed with CGAL.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL: svn+ssh://scm.gforge.inria.fr/svn/cgal/branches/CGAL-3.2-branch/Convex_hull_2/include/CGAL/ch_graham_andrew.C $
// $Id: ch_graham_andrew.C 28567 2006-02-16 14:30:13Z lsaboret $
//
//
// Author(s) : Stefan Schirra
#ifndef CGAL_CH_GRAHAM_ANDREW_C
#define CGAL_CH_GRAHAM_ANDREW_C
#ifndef CGAL_CH_GRAHAM_ANDREW_H
#include <CGAL/ch_graham_andrew.h>
#endif // CGAL_CH_GRAHAM_ANDREW_H
#ifndef CGAL_CH_NO_POSTCONDITIONS
#include <CGAL/convexity_check_2.h>
#endif // CGAL_CH_NO_POSTCONDITIONS
#include <CGAL/ch_assertions.h>
#include <CGAL/algorithm.h>
#include <CGAL/IO/Tee_for_output_iterator.h>
#include <vector>
#include <algorithm>
CGAL_BEGIN_NAMESPACE
template <class BidirectionalIterator, class OutputIterator, class Traits>
OutputIterator
ch_graham_andrew_scan( BidirectionalIterator first,
BidirectionalIterator last,
OutputIterator result,
const Traits& ch_traits)
{
typedef typename Traits::Less_xy_2 Less_xy;
typedef typename Traits::Point_2 Point_2;
typedef typename Traits::Left_turn_2 Left_turn;
std::vector< BidirectionalIterator > S;
BidirectionalIterator alpha;
BidirectionalIterator beta;
BidirectionalIterator iter;
CGAL_ch_precondition( first != last );
CGAL_ch_precondition( successor(first) != last );
--last;
CGAL_ch_precondition( *first != *last );
S.push_back( last );
S.push_back( first );
Left_turn left_turn = ch_traits.left_turn_2_object();
iter = first;
do
{
++iter;
}
while (( iter != last ) && !left_turn(*last, *first, *iter) );
if ( iter != last )
{
S.push_back( iter );
typedef typename std::vector<BidirectionalIterator>::reverse_iterator
rev_iterator;
rev_iterator stack_rev_iter = S.rbegin();
alpha = iter;
beta = *++stack_rev_iter;
for ( ++iter ; iter != last; ++iter )
{
if ( left_turn(*alpha, *iter, *last) )
{
while ( !left_turn(*beta, *alpha, *iter) )
{
S.pop_back();
alpha = beta;
stack_rev_iter = S.rbegin();
beta = *++stack_rev_iter;
CGAL_ch_assertion(S.size() >= 2);
}
S.push_back( iter );
beta = alpha;
alpha = iter;
}
}
}
typedef typename std::vector< BidirectionalIterator >::iterator std_iterator;
std_iterator stack_iter = S.begin();
#if defined(CGAL_CH_NO_POSTCONDITIONS) || defined(CGAL_NO_POSTCONDITIONS) \
|| defined(NDEBUG)
OutputIterator res(result);
#else
Tee_for_output_iterator<OutputIterator,Point_2> res(result);
#endif // no postconditions ...
for ( ++stack_iter; stack_iter != S.end(); ++stack_iter)
{ *res = **stack_iter; ++res; }
CGAL_ch_postcondition( \
is_ccw_strongly_convex_2( res.output_so_far_begin(), \
res.output_so_far_end(), \
ch_traits));
CGAL_ch_expensive_postcondition( \
ch_brute_force_chain_check_2( \
first, last, \
res.output_so_far_begin(), res.output_so_far_end(), \
ch_traits));
#if defined(CGAL_CH_NO_POSTCONDITIONS) || defined(CGAL_NO_POSTCONDITIONS) \
|| defined(NDEBUG)
return res;
#else
return res.to_output_iterator();
#endif // no postconditions ...
}
template <class BidirectionalIterator, class OutputIterator, class Traits>
OutputIterator
ch__ref_graham_andrew_scan( BidirectionalIterator first,
BidirectionalIterator last,
OutputIterator& result,
const Traits& ch_traits)
{
typedef typename Traits::Less_xy_2 Less_xy;
typedef typename Traits::Point_2 Point_2;
typedef typename Traits::Left_turn_2 Left_turn;
CGAL_ch_precondition_code(
typedef typename Traits::Equal_2 Equal_2;
Equal_2 equal_points = ch_traits.equal_2_object();
)
Left_turn left_turn = ch_traits.left_turn_2_object();
std::vector< BidirectionalIterator > S;
BidirectionalIterator alpha;
BidirectionalIterator beta;
BidirectionalIterator iter;
CGAL_ch_precondition( first != last );
CGAL_ch_precondition( successor(first) != last );
--last;
CGAL_ch_precondition(! equal_points(*first,*last) );
S.push_back( last );
S.push_back( first );
iter = first;
do
{
++iter;
}
while (( iter != last ) && !left_turn(*last, *first, *iter) );
if ( iter != last )
{
S.push_back( iter );
typedef typename std::vector<BidirectionalIterator>::reverse_iterator
rev_iterator;
rev_iterator stack_rev_iter = S.rbegin();
alpha = iter;
beta = *++stack_rev_iter;
for ( ++iter ; iter != last; ++iter )
{
if ( left_turn(*alpha, *iter, *last) )
{
while ( !left_turn(*beta, *alpha, *iter) )
{
S.pop_back();
alpha = beta;
stack_rev_iter = S.rbegin();
beta = *++stack_rev_iter;
CGAL_ch_assertion(S.size() >= 2);
}
S.push_back( iter );
beta = alpha;
alpha = iter;
}
}
}
typedef typename std::vector< BidirectionalIterator >::iterator std_iterator;
std_iterator stack_iter = S.begin();
for ( ++stack_iter; stack_iter != S.end(); ++stack_iter)
{ *result = **stack_iter; ++result; }
return result;
}
template <class InputIterator, class OutputIterator, class Traits>
OutputIterator
ch_graham_andrew( InputIterator first,
InputIterator last,
OutputIterator result,
const Traits& ch_traits)
{
typedef typename Traits::Less_xy_2 Less_xy;
typedef typename Traits::Point_2 Point_2;
typedef typename Traits::Left_turn_2 Left_turn;
typedef typename Traits::Equal_2 Equal_2;
Equal_2 equal_points = ch_traits.equal_2_object();
if (first == last) return result;
std::vector< Point_2 > V;
std::copy( first, last, std::back_inserter(V) );
std::sort( V.begin(), V.end(), ch_traits.less_xy_2_object() );
if (equal_points( *(V.begin()), *(V.rbegin())) )
{
*result = *(V.begin()); ++result;
return result;
}
#if defined(CGAL_CH_NO_POSTCONDITIONS) || defined(CGAL_NO_POSTCONDITIONS) \
|| defined(NDEBUG)
OutputIterator res(result);
#else
Tee_for_output_iterator<OutputIterator,Point_2> res(result);
#endif // no postconditions ...
ch__ref_graham_andrew_scan( V.begin(), V.end(), res, ch_traits);
ch__ref_graham_andrew_scan( V.rbegin(), V.rend(), res, ch_traits);
CGAL_ch_postcondition( \
is_ccw_strongly_convex_2( res.output_so_far_begin(), \
res.output_so_far_end(), \
ch_traits));
CGAL_ch_expensive_postcondition( \
ch_brute_force_check_2( \
V.begin(), V.end(), \
res.output_so_far_begin(), res.output_so_far_end(), \
ch_traits));
#if defined(CGAL_CH_NO_POSTCONDITIONS) || defined(CGAL_NO_POSTCONDITIONS) \
|| defined(NDEBUG)
return res;
#else
return res.to_output_iterator();
#endif // no postconditions ...
}
template <class InputIterator, class OutputIterator, class Traits>
OutputIterator
ch_lower_hull_scan( InputIterator first,
InputIterator last,
OutputIterator result,
const Traits& ch_traits)
{
typedef typename Traits::Less_xy_2 Less_xy;
typedef typename Traits::Point_2 Point_2;
typedef typename Traits::Left_turn_2 Left_turn;
typedef typename Traits::Equal_2 Equal_2;
Equal_2 equal_points = ch_traits.equal_2_object();
if (first == last) return result;
std::vector< Point_2 > V;
std::copy( first, last, std::back_inserter(V) );
std::sort( V.begin(), V.end(), ch_traits.less_xy_2_object() );
if (equal_points( *(V.begin()), *(V.rbegin())) )
{
*result = *(V.begin()); ++result;
return result;
}
#if defined(CGAL_CH_NO_POSTCONDITIONS) || defined(CGAL_NO_POSTCONDITIONS) \
|| defined(NDEBUG)
OutputIterator res(result);
#else
Tee_for_output_iterator<OutputIterator,Point_2> res(result);
#endif // no postconditions ...
ch_graham_andrew_scan( V.begin(), V.end(), res, ch_traits);
#if defined(CGAL_CH_NO_POSTCONDITIONS) || defined(CGAL_NO_POSTCONDITIONS) \
|| defined(NDEBUG)
return res;
#else
return res.to_output_iterator();
#endif // no postconditions ...
}
template <class InputIterator, class OutputIterator, class Traits>
OutputIterator
ch_upper_hull_scan( InputIterator first,
InputIterator last,
OutputIterator result,
const Traits& ch_traits)
{
typedef typename Traits::Less_xy_2 Less_xy;
typedef typename Traits::Point_2 Point_2;
typedef typename Traits::Left_turn_2 Left_turn;
typedef typename Traits::Equal_2 Equal_2;
Equal_2 equal_points = ch_traits.equal_2_object();
if (first == last) return result;
std::vector< Point_2 > V;
std::copy( first, last, std::back_inserter(V) );
std::sort( V.begin(), V.end(), ch_traits.less_xy_2_object() );
if (equal_points( *(V.begin()), *(V.rbegin())) )
{ return result; }
#if defined(CGAL_CH_NO_POSTCONDITIONS) || defined(CGAL_NO_POSTCONDITIONS) \
|| defined(NDEBUG)
OutputIterator res(result);
#else
Tee_for_output_iterator<OutputIterator,Point_2> res(result);
#endif // no postconditions ...
ch_graham_andrew_scan( V.rbegin(), V.rend(), res, ch_traits);
#if defined(CGAL_CH_NO_POSTCONDITIONS) || defined(CGAL_NO_POSTCONDITIONS) \
|| defined(NDEBUG)
return res;
#else
return res.to_output_iterator();
#endif // no postconditions ...
}
CGAL_END_NAMESPACE
#endif // CGAL_CH_GRAHAM_ANDREW_C
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