Neighbors find_neighbors_bruteforce_impl(const RandomAccessIterator& begin, const RandomAccessIterator& end,
Callback callback, IndexType k)
{
timed_context context("Distance sorting based neighbors search");
typedef std::pair<RandomAccessIterator, ScalarType> DistanceRecord;
typedef std::vector<DistanceRecord> Distances;
Neighbors neighbors;
neighbors.reserve(end-begin);
for (RandomAccessIterator iter=begin; iter!=end; ++iter)
{
Distances distances;
for (RandomAccessIterator around_iter=begin; around_iter!=end; ++around_iter)
distances.push_back(std::make_pair(around_iter, callback.distance(iter,around_iter)));
std::nth_element(distances.begin(),distances.begin()+k+1,distances.end(),
distances_comparator<DistanceRecord>());
LocalNeighbors local_neighbors;
local_neighbors.reserve(k);
for (typename Distances::const_iterator neighbors_iter=distances.begin();
neighbors_iter!=distances.begin()+k+1; ++neighbors_iter)
{
if (neighbors_iter->first != iter)
local_neighbors.push_back(neighbors_iter->first - begin);
}
neighbors.push_back(local_neighbors);
}
return neighbors;
}
int main () {
std::cout << "Graph example program "
<< " - find shortest path in a directed graph."
<< std::endl;
static const char pendleton[] = "Pendleton";
static const char pensacola[] = "Pensacola";
static const char peoria[] = "Peoria";
static const char phoenix[] = "Phoenix";
static const char pierre[] = "Pierre";
static const char pittsburgh[] = "Pittsburgh";
static const char princeton[] = "Princeton";
static const char pueblo[] = "Pueblo";
Cities cityMap;
cityMap[pendleton][phoenix] = 4;
cityMap[pendleton][pueblo] = 8;
cityMap[pensacola][phoenix] = 5;
cityMap[peoria][pittsburgh] = 5;
cityMap[peoria][pueblo] = 3;
cityMap[phoenix][peoria] = 4;
cityMap[phoenix][pittsburgh] = 10;
cityMap[phoenix][pueblo] = 3;
cityMap[pierre][pendleton] = 2;
cityMap[pittsburgh][pensacola] = 4;
cityMap[princeton][pittsburgh] = 2;
cityMap[pueblo][pierre] = 3;
Distances dist;
shortestDistance (cityMap, pierre, dist);
Distances::iterator where;
std::cout << "Find the shortest path from : "
<< pierre << '\n';
for (where = dist.begin (); where != dist.end (); ++where)
std::cout << " Distance to: " << (*where).first << ":"
<< (*where).second << '\n';
std::cout << "End of graph example program" << '\n';
return 0;
}
