\( \newcommand{\E}{\mathrm{E}} \) \( \newcommand{\A}{\mathrm{A}} \) \( \newcommand{\R}{\mathrm{R}} \) \( \newcommand{\N}{\mathrm{N}} \) \( \newcommand{\Q}{\mathrm{Q}} \) \( \newcommand{\Z}{\mathrm{Z}} \) \( \def\ccSum #1#2#3{ \sum_{#1}^{#2}{#3} } \def\ccProd #1#2#3{ \sum_{#1}^{#2}{#3} }\)

CGAL 4.8 - 2D Convex Hulls and Extreme Points

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Convex_hull_2/ch_graham_anderson.cpp
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/ch_graham_andrew.h>
#include <vector>
#include <algorithm>
#include <boost/bind.hpp>
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef K::Point_2 Point_2;
template <class InputIterator, class OutputIterator, class Traits>
OutputIterator
ch_graham_anderson( InputIterator first, InputIterator beyond,
OutputIterator result, const Traits& ch_traits)
{
using namespace boost;
typedef typename Traits::Point_2 Point_2;
typedef typename Traits::Less_xy_2 Less_xy_2;
typedef typename Traits::Less_rotate_ccw_2 Less_rotate_ccw_2;
if (first == beyond) return result;
std::vector< Point_2 > V (first, beyond);
typename std::vector< Point_2 >::iterator it =
std::min_element(V.begin(), V.end(), Less_xy_2());
std::sort( V.begin(), V.end(), boost::bind(Less_rotate_ccw_2(), *it, _1, _2) );
if ( *(V.begin()) != *(V.rbegin()) )
{
result = CGAL::ch_graham_andrew_scan( V.begin(), V.end(), result, ch_traits);
}
// add the last point of the sequence that is
// not added by ch_graham_andrew_scan
*result++ = *(V.rbegin());
return result;
}
int main()
{
CGAL::set_ascii_mode(std::cin);
CGAL::set_ascii_mode(std::cout);
std::istream_iterator< Point_2 > in_start( std::cin );
std::istream_iterator< Point_2 > in_end;
std::ostream_iterator< Point_2 > out( std::cout, "\n" );
ch_graham_anderson(in_start, in_end, out, K());
return 0;
}