初学者在2D网格上与Lee算法斗争

Question

我试图在2D网格上实现Lee算法。然而，洪水循环太早停止，声称没有找到任何更多的“空”细胞。我完全不知道为什么。

class LocalNotificationViewController: UIViewController {
    var timer = Timer()

    func runTimer() {
        timer = Timer.scheduledTimer(timeInterval: 5, target: self, selector: (#selector(self.setLocalNotification)), userInfo: nil, repeats: true)
    }

    @objc func setLocalNotification() {
        //        timeEntered = time.text!
        //        let hrMin = timeEntered.components(separatedBy: ":");
        let content = UNMutableNotificationContent()
        content.title = "Test Local Notification"
        content.subtitle = "Testing..."
        content.body = "Testing..."
        content.badge = 1
        content.sound = UNNotificationSound(named: "alarm.aiff");

            trigger = UNTimeIntervalNotificationTrigger(timeInterval: 5, repeats: false);

            let request = UNNotificationRequest(identifier: "timerDone", content: content, trigger: trigger)

            UNUserNotificationCenter.current().add(request, withCompletionHandler: nil)
    }

    var timeEntered: String = "";
    var trigger: UNTimeIntervalNotificationTrigger? = nil;
    @IBOutlet var time: UITextField!;

    @IBAction func setNotification(_ sender: Any) {
        runTimer()
    }

    @IBAction func stopRepeat(_ sender: Any) {
        timer.invalidate()
    }

通过将单元格指定给-3来指定路径上的结尾。被阻止的细胞是-2。空的单元格是-1。起始单元格为0。

Answer 1

不确定您的问题是什么，但您的算法似乎很稳定。我已经清理了一下它似乎工作正常：

#include <iostream>
#include <string>
#include <iomanip>

#define WIDTH 7
#define HEIGHT 7 

int gridArray[WIDTH][HEIGHT] = 
{
    { -1,-1,-1,0,-2,-1,-2 },
    { -2,-1,-1,-1,-1,-2,-2 },
    { -2,-1,-1,-1,-1,-2,-2 },
    { -2,-2,-1,-1,-1,-2,-1 },
    { -1,-2,-2,-2,-1,-1,-2 },
    { -1,-2,-1,-1,-1,-2,-2 },
    { -2,-2,-3,-1,-1,-2,-2 }
};

void DrawGrid() 
{
    for (int x = 0; x < WIDTH; x++)  
    {
        for (int y = 0; y < HEIGHT; y++)
        {
            std::string message;

            if (gridArray[x][y] == 0)
                message = "S";
            else if (gridArray[x][y] == -3)
                message = "E";
            else if (gridArray[x][y] == -2)
                message = "#";
            else if (gridArray[x][y] == -1)
                message = ".";
            else
                message = std::to_string(gridArray[x][y]);

            std::cout << std::setw(3) << message << "  ";
        }
        std::cout << std::endl << std::endl;
    }
    std::cout << std::endl << std::endl;
}

void SolveMaze()
{
    bool foundEnd = false;
    int it = 0;

    while (!foundEnd) 
    {
        bool foundEmpty = false;
        for (int x = 0; x < WIDTH && !foundEnd; ++x)
        {
            for (int y = 0; y < HEIGHT; ++y)
            {
                if (gridArray[x][y] == it) 
                {
                    // check east cell
                    if (x < WIDTH - 1)
                    {
                        int &east = gridArray[x + 1][y];
                        if (east == -3)
                        {
                            foundEnd = true;
                            break;
                        }
                        else if (east == -1)
                        {
                            east = it + 1;
                            foundEmpty = true;
                        }
                    }

                    // check west cell
                    if (x > 0)
                    {
                        int &west = gridArray[x - 1][y];
                        if (west == -3)
                        {
                            foundEnd = true;
                            break;
                        }
                        else if (west == -1)
                        {
                            west = it + 1;
                            foundEmpty = true;
                        }
                    }

                    // check south cell
                    if (y < HEIGHT - 1)
                    {
                        int &south = gridArray[x][y + 1];
                        if (south == -3)
                        {
                            foundEnd = true;
                            break;
                        }
                        else if (south == -1)
                        {
                            south = it + 1;
                            foundEmpty = true;
                        }
                    }

                    // check north cell
                    if (y > 0)
                    {
                        int &north = gridArray[x][y - 1];
                        if (north == -3)
                        {
                            foundEnd = true;
                            break;
                        }
                        else if (north == -1)
                        {
                            north = it + 1;
                            foundEmpty = true;
                        }
                    }   
                }
            }
        }

        if (!foundEnd && !foundEmpty)
        {
            std::cout << "This maze has no solution!" << std::endl << std::endl;
            break;
        }

        it++;
    }
}

int main()
{
    DrawGrid();
    SolveMaze();
    DrawGrid();
    system("pause");
    return 0;
}