osrm-backend/include/engine/trip/trip_brute_force.hpp

#ifndef TRIP_BRUTE_FORCE_HPP
#define TRIP_BRUTE_FORCE_HPP

#include "util/dist_table_wrapper.hpp"
#include "util/simple_logger.hpp"
#include "util/typedefs.hpp"

#include "osrm/json_container.hpp"

#include <algorithm>
#include <cstdlib>
#include <iterator>
#include <limits>
#include <string>
#include <vector>

namespace osrm
{
namespace engine
{
namespace trip
{

// computes the distance of a given permutation
EdgeWeight ReturnDistance(const util::DistTableWrapper<EdgeWeight> &dist_table,
                          const std::vector<NodeID> &location_order,
                          const EdgeWeight min_route_dist,
                          const std::size_t component_size)
{
    EdgeWeight route_dist = 0;
    std::size_t i = 0;
    while (i < location_order.size() && (route_dist < min_route_dist))
    {
        route_dist += dist_table(location_order[i], location_order[(i + 1) % component_size]);
        BOOST_ASSERT_MSG(dist_table(location_order[i], location_order[(i + 1) % component_size]) !=
                             INVALID_EDGE_WEIGHT,
                         "invalid route found");
        ++i;
    }

    return route_dist;
}

// computes the route by computing all permutations and selecting the shortest
template <typename NodeIDIterator>
std::vector<NodeID> BruteForceTrip(const NodeIDIterator start,
                                   const NodeIDIterator end,
                                   const std::size_t number_of_locations,
                                   const util::DistTableWrapper<EdgeWeight> &dist_table)
{
    (void)number_of_locations; // unused

    const auto component_size = std::distance(start, end);

    std::vector<NodeID> perm(start, end);
    std::vector<NodeID> route;
    route.reserve(component_size);

    EdgeWeight min_route_dist = INVALID_EDGE_WEIGHT;

    // check length of all possible permutation of the component ids

    BOOST_ASSERT_MSG(perm.size() > 0, "no permutation given");
    BOOST_ASSERT_MSG(*(std::max_element(std::begin(perm), std::end(perm))) < number_of_locations,
                     "invalid node id");
    BOOST_ASSERT_MSG(*(std::min_element(std::begin(perm), std::end(perm))) >= 0, "invalid node id");

    do
    {
        const auto new_distance = ReturnDistance(dist_table, perm, min_route_dist, component_size);
        if (new_distance <= min_route_dist)
        {
            min_route_dist = new_distance;
            route = perm;
        }
    } while (std::next_permutation(std::begin(perm), std::end(perm)));

    return route;
}
}
}
}

#endif // TRIP_BRUTE_FORCE_HPP