安卓app 地铁最短路径查询（迪杰斯特拉算法） 完成

合集 - 结对作业(3)

1.首次结对合作2024-03-272.地铁查询app 结对作业三2024-03-28

3.安卓app 地铁最短路径查询（迪杰斯特拉算法） 完成2024-03-29

收起

 我通过三个函数 完成了这个功能

首先  创建哈希表 根据起始站名 终点站名

然后 根据哈希表 建立起 邻接表‘

最后 根据迪杰斯特拉算法 完成这个功能

 /**
     * function：起终查询
     */
    // 构建邻接表
    public static Map<String, Map<String, Integer>> buildAdjacencyList() {
        Connection connection = JDBCUtils.getConn();
        Map<String, Map<String, Integer>> adjacencyList = new HashMap<>();

        try {
            Statement statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery("SELECT Starting_Station, Terminus_Station FROM station");

            while (resultSet.next()) {

                String startingStation = resultSet.getString("Starting_Station");
                String terminusStation = resultSet.getString("Terminus_Station");

                addConnection(adjacencyList, startingStation, terminusStation);
                addConnection(adjacencyList, terminusStation, startingStation);
            }

            resultSet.close();
            statement.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
            // 适当处理 SQLException
        }

        return adjacencyList;
    }



    // 将连接添加到邻接表
    private static void addConnection(Map<String, Map<String, Integer>> adjacencyList, String source, String destination) {
        if (!adjacencyList.containsKey(source))
        {
            adjacencyList.put(source, new HashMap<>());
        }
        adjacencyList.get(source).put(destination, 1);
    }


    //根据 buildAdjacencyList（）函数 求邻接表 最短路径
    public static List<String> shortest(User user) {
        String startingStation = user.getStarting_Station();
        String terminusStation = user.getTerminus_Station();

        Map<String, Map<String, Integer>> adjacencyList = buildAdjacencyList();
        Map<String, Integer> distance = new HashMap<>();
        Map<String, String> previous = new HashMap<>();
        PriorityQueue<String> queue = new PriorityQueue<>(Comparator.comparingInt(distance::get));

        for (String station : adjacencyList.keySet()) {
            distance.put(station, Integer.MAX_VALUE);
            previous.put(station, null);
        }

        distance.put(startingStation, 0);
        queue.add(startingStation);

        while (!queue.isEmpty()) {
            String currentStation = queue.poll();
            if (currentStation.equals(terminusStation)) {
                break; // Found shortest path to terminus station
            }

            Map<String, Integer> neighbors = adjacencyList.get(currentStation);
            if (neighbors != null) {
                for (String neighbor : neighbors.keySet()) {
                    int alt = distance.get(currentStation) + neighbors.get(neighbor);
                    if (alt < distance.get(neighbor)) {
                        distance.put(neighbor, alt);
                        previous.put(neighbor, currentStation);
                        queue.add(neighbor);
                    }
                }
            }
        }

        // Reconstruct shortest path
        List<String> shortestPath = new ArrayList<>();
        String current = terminusStation;
        while (previous.get(current) != null) {
            shortestPath.add(current);
            current = previous.get(current);
        }
        shortestPath.add(startingStation);
        Collections.reverse(shortestPath);

        System.out.println(shortestPath);

        return shortestPath;

    }