// Finds routes from start to end with a length shorter than the limit.
public List <Route> FindRoutesShorterThan(char start, char end, int limit)
{
// List of routes that need to be explored further.
List <Route> explore_routes = new List <Route>();
// Initialize the explore_routes list with the starting city.
List <char> starting_city = new List <char>()
{
start
};
explore_routes.Add(new Route(starting_city, 0));
// List of routes shorter than limit.
List <Route> found_routes = new List <Route>();
// Search until there are no more potential routes that could be less than the limit.
while (explore_routes.Count > 0)
{
// List of routes to explore after the current list.
List <Route> explore_routes_next = new List <Route>();
// For each route in the routes to explore.
foreach (Route route in explore_routes)
{
// Find the last city in the current route.
int current_city_index = route.cities.Count - 1;
char current_city = route.cities[current_city_index];
// Find each edge starting from the end of the current route.
foreach (Edge edge in edges)
{
// if the edge starts in the current city in the route
if (edge.start == current_city)
{
// Add a new route, the same as the current one, but with this edge added to the route.
Route new_route = route.DeepCopy();
new_route.cities.Add(edge.end);
new_route.length += edge.length;
// If the new route is less than the limit.
if (new_route.length < limit)
{
// If edge leads to the end city.
if (edge.end == end)
{
// Add to found route list
found_routes.Add(new_route);
}
// Add all new routes to list of routes to explore further.
explore_routes_next.Add(new_route);
}
}
}
}
// These routes don't end at the correct city, but still could potentially lead to the city while under the limit.
explore_routes = explore_routes_next;
}
return(found_routes);
}
// Finds the length of the shortest route from start to end.
public string FindShortestRouteLength(char start, char end)
{
// List of routes that are still being explored
List <Route> explore_routes = new List <Route>();
List <char> starting_city = new List <char>()
{
start
};
explore_routes.Add(new Route(starting_city, 0));
// initialize at max integer.
int shortest_route_length = 2147483647;
// Search until there are no more potentially shorter routes left in the explore_routes list.
while (explore_routes.Count > 0)
{
// List of routes to explore after the current list.
List <Route> explore_routes_next = new List <Route>();
// For each route find potential next edge
foreach (Route route in explore_routes)
{
int current_city_index = route.cities.Count - 1;
char current_city = route.cities[current_city_index];
// Find each edge starting from the end of the current route.
foreach (Edge edge in edges)
{
// if the edge starts in the current city in the route
if (edge.start == current_city)
{
// The following if condition exists, because the fastest route is never going to the same city twice.
// if the edge doesn't lead to a city already in the route or leads to the starting city.
if (route.cities.IndexOf(edge.end) == -1 || route.cities.IndexOf(edge.end) == 0)
{
// Add a new route, the same as the current one, but with this edge added to the route.
Route new_route = route.DeepCopy();
new_route.cities.Add(edge.end);
new_route.length += edge.length;
if (new_route.length < shortest_route_length)
{
// If edge leads to the end city.
if (edge.end == end)
{
// Set new shortest length.
shortest_route_length = new_route.length;
}
else
{
// Add to list of routes to explore further.
explore_routes_next.Add(new_route);
}
}
}
}
}
}
// These routes don't end at the correct city, but still could potentially lead to a shorter path.
explore_routes = explore_routes_next;
}
string shortest_route_length_string;
if (shortest_route_length == 2147483647)
{
shortest_route_length_string = "NO SUCH ROUTE";
}
else
{
shortest_route_length_string = shortest_route_length.ToString();
}
return(shortest_route_length_string);
}
