osrm-backend/routing_algorithms/tsp_brute_force.hpp

/*

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*/

#ifndef TSP_BRUTE_FORCE_HPP
#define TSP_BRUTE_FORCE_HPP


#include "../data_structures/search_engine.hpp"
#include "../util/string_util.hpp"

#include <osrm/json_container.hpp>

#include <cstdlib>

#include <algorithm>
#include <string>
#include <vector>
#include <limits>
#include <iostream>
#include "../util/simple_logger.hpp"




namespace osrm
{
namespace tsp
{

template <typename number>
int ReturnDistance(const std::vector<EdgeWeight> & dist_table,
                   const std::vector<number> & location_order,
                   const EdgeWeight min_route_dist,
                   const int number_of_locations) {
    int route_dist = 0;
    int i = 0;
    while (i < location_order.size() - 1) {
        route_dist += *(dist_table.begin() + (location_order[i] * number_of_locations) + location_order[i+1]);
        ++i;
    }
    //get distance from last location to first location
    route_dist += *(dist_table.begin() + (location_order[location_order.size()-1] * number_of_locations) + location_order[0]);
    return route_dist;
}

std::vector<NodeID> BruteForceTSP(std::vector<NodeID> & component,
                                  const std::size_t number_of_locations,
                                  const std::vector<EdgeWeight> & dist_table) {

    std::vector<NodeID> route;
    route.reserve(number_of_locations);


    EdgeWeight min_route_dist = INVALID_EDGE_WEIGHT;

    // check length of all possible permutation of the component ids
    do {
        const auto new_distance = ReturnDistance(dist_table, component, min_route_dist, number_of_locations);
        if (new_distance <= min_route_dist) {
            min_route_dist = new_distance;
            route = component;
        }
    } while(std::next_permutation(component.begin(), component.end()));

    return route;
}

} //end namespace osrm
} //end namespace tsp
#endif // TSP_BRUTE_FORCE_HPP